Muktol

One of the first decks I built here (for a friend) was a counter-transfer deck (http://www.mtgvault.com/muktol/decks/counter-transfer/)

Some suggestions from there:
"Power Conduit"...helps you to transfer counters from A to B
"Chalice of the Void"...as I am able to easily transfer counters, I can play around the effect of this artifact, but for my opponent its a pain in the ass
"Surge Node" and "Chronozoa"...Surge Node is a counter-safe from where you can move counters onto another object. Chronozoa needs a little help, like "Power Conduit" but is has unlimited counters and also helps you to stay alive. But it has a antisynergy with more than one "Paradox haze" as you will never be able to attack with them.
Titan Forge...combined with "Wing Splicer" it could solve as a second win option
Etherium Sculptor...lowers the cost of all artifact spells and can serve as defender in early games
Thoughtcast...cheap carddraw if you have enough artifacts out.

Greetings
Muktol

Just for Info, the whole Innistrad block and M13 got rotated out of standard with the apperance of Theros. If you want to play it in modern there are a few things i would change.

I know, I made a standard discard deck some days ago (I knew that Innistrad and M13 was rotated out) and nevertheless got 2 illegal cards in. Posted the deck on another site and this was the first thing the guys pointed out: ILLEGAL CARDS *g*

Demons Horn -> M12
Endless Ranks of the Dead -> Innistrad
Mikaeus, the Unhallowed -> Dark Ascension
All of your sorcerys

http://www.wizards.com/magic/magazine/article.aspx?x=judge/resources/sfrstandard
MTGVault is a little slow rotating the complete Innistrad cycle and M13 out of the standard block

Ups, didn't see the Loyalist, sorry.
I normally suggest using (2-)3 Krenko's (as with all legendarys) as he gets shot away faster than you can say Bolt.
The idea behind the second "Siege-Gang Commander" is to have a good target for "Warren Instigator". You can always cast a cc1 creature, but to bring a cc3+ into play for zero is a different thing ;)
Greetings
Muktol

Some suggestions based on my own Goblin deck (http://www.mtgvault.com/muktol/decks/monor-tribal-goblins/)

I would remove both "Shock" for 1 or 2 more "Krenko, Mob Boss" and/ or 1 more "Siege-Gang Commander"
Furthermore I would change from "Goblin Arsonist" to "Legion Loyalist"
You could also think of removing 1-2 mountains as your mana-curve is very low.

Greetings
Muktol

The next question is, do you want to create a EDH deck that is good in 1vs1 or multi-player?
From what I know Commander Decks are full of board sweepers (aka mass descruction) so you may need something to counter this or to get your creatures back from your graveyard.
Also spells that can be used again, with keywords like 'unearth' or 'flashback', are better here than normal spells. And I would also use some turors, to get key-creatures that you need....Diabolic Tutor or creatures with 'transmute'
...just some things that got into my mind till yesterday

I'm no expert on EDH but with just 3 red cards I would either change to MonoB or add some more red or red/black cards to benefit from the red-splash.

Dimir Infiltrator...I would try to do a 3/3 split between "Dimir Infiltrator" and "Invisible Stalker". The Infiltrator has the advantage of being able to tutor you a cc3 creature that you need, if you don't need a enabler for your ninjutsu at the moment
Higure, the Still Wind...Raise up to 3 as this is one of your best ninjas. No more since he is legendary and is out of bolt range.
Ink-Eyes, Servant of Oni...Reduce to to 1. You can tutor him with Higure and since you will play him with ninjutsu he will at last attacke once, which can be enough to win the game.
Minamo Sightbender...I would remove him since I am a fan of "Artful Dodge" (See suggestions)
Mistblade Shinobi...Raise up to 4, as they are cheap and keep your opponent with a hand full of creatures but none on the table.
Silent-Blade Oni...If you want to stay modern legal you have to remove him.
"Dimir Charm" and "Mana Leak"...I would rather play some point removals and pherhaps some counters in my sideboard. If you want some counters take a look at "Essence Scatter", "Negate" and "Familliar's Ruse" (See suggestions)

Some suggestions from my own U/B Ninja deck (http://www.mtgvault.com/muktol/decks/ub-tribal-ninjas/)
Ronin Warclub (cc3, +2/+1, attaches automaticly to any of your creatures entering the board e.g. ninjutsu ninjas)
Ornithopter (cc0, 0/2 fyling, I play him as second enabler and sideboard to "Dimir Infiltrator" if my opponent hast some flyers)
Doom Blade (cc2, point removal, alternative would be "Go for the Throat"), Familiar's Ruse (return a creature you control to your hand hand, Counter target spell), Far // Away (Return target creature to its owner's hand. // Target player sacrifices a creature), Artful Dodge (cc1 target creature is unblockable this turn, flahsback cc1)
Dimir Aqueduct (Dualland), Jwar Isle Refuge (Dualland)

i hope I was able to help you a little bit
Greetings
Muktol

I would change some numbers and remove some creatures here
"Falkenrath Exterminator"...Remove. Without propper support, e.g. "Blade of the Bloodchief" or a huge amount of removal, he won't be able to get those counters you need for him.
"Guul Draz Assassin"...Remove. It sounds great, but in the end you have to pay 5 mana and 1 mana every turn to remove a 2/2 creature from your opponent, thus costs to much in my oppinion.
"Guul Draz Vampire"...I would decide either to take "Guul Draz Vampire" or "Stromkirk Noble" and remove the other one. The Noble has the advantage of being able to collect counters all allone, the Guul Draz becomes stronger when you have damaged your opponent allready.
"Dash Hopes"...I don't know how useful a counter can be here especially if you have only 2 of those.
"Murder"...Remove. There are better point removals
"Urge to Feed"...I'm no fan of this card. You can remove a 3/3 for 2 mana and tap many of your vampires, but this will leave you wide open for a counterattack.
"Feast of Blood"...often enough it was hard for me to meet the requirements to cast this spell.

Try to raise the numbers of most of your cards to 4, as you wan't to draw them and if one gets removed, you still have 3 other of it in your deck. It also raises the chance of drawing it.
You could also try to reduce the number of lands to 22 or 20 as you don't have many high-cost spell.

Some suggestions from my own B/R Vampire deck (http://www.mtgvault.com/muktol/decks/br-tribal-vampire/)
Blade of the Bloodchief (cc1, equip 1, whenever a creature dies, equiped vampire gets 2 +1/+1 counters)
Bloodghast (cc2, 2/1, cant block, comes again from the graveyard if you play a land), Bloodline Keeper (cc4, 3/3 flying, if you control 5 or more vampires flip huim -> vampires get +2/+2), Vampire Nocturnus (Top card of your library is open. As long as it is black, Vampires you control get +2/+1 and have flying), Bloodlord of Vaasgoth (cc5, 3/3 flying, all your vampire spells get Bloodlust 3)
Curse of Stalked Prey (Alternative to Rakish Heir. Harder to remove but you loose a possible blocker), Go for the Throat (Pointremoval, hits anything but artifactcreatures), Lightning Bolt (cc1, 3 damage), Terminate (Pointremoval, hits anything and target can't regenerate), Dreadbore (Pointremoval, hits anything and planeswalkers)
Blackcleave Cliffs (Dualland), Graven Cairns (Dualland)

I hope I was able to help you a little bit
Greetings
Muktol

"Howl of the Nightpackt" proofed to be to expensive. When I had the mana, I played "Primeval Titan" and searched for "Inkmoth Nexus" and "Kessig Wolf Run" and pumped the flying Nexus.

I also had him in the first version of this deck. But back then I used less creatures that I could sac and thus often had to exile him, as he was the only creature on the field when he came back with 'Undying'.

Thank you for your suggestions

I Used "Gravecrawler" earlier, but as I removed most of my other zombies from the deck I wasn't sure that I could cast him from the graveyard. I also had "Barther in Blood" in the deck earlier, but it proofed to be to expensive to play here.
I will give "Gravepackt", "Mutilate" and "Altar's Reap" a try, I was thinking about "Sign in Blood" as carddraw, but this fits better to the sacrifice theme.

Thanks for the suggestion. I will give "Howl of the Night Pack" and "Primal Bellow" a try.

I would try "Pulse Tracker" instead. Does the same damage but without the drawback in life
Oh and I would cut the "Markov Blademaster". Its a great card but too slow. It needs massive support to get through. Also you could lower the number of "Dark Impostor" to 2 or 3, his ability is rather expensive to use and thus you don't want him more than once or twice on the field.

Ups, "Sanity Grinding" is opponent only. Sorry, thought it was target player :)

Depending on your average mana costs you could try to reduce the number of lands to 20 or even 18.

Some suggestions from my own modern goblin ceck (http://www.mtgvault.com/muktol/decks/monor-tribal-goblins/)
Furystoke Giant (Finisher), Mogg War Marshal (Comes with a little friend, great to use with ETB effects), Siege-Gang Commander (Can convert goblins into damage), Spikeshot Elder (Cheaper than "Lightning Crafter" but buffed equal potent. can be used multiple times), Warren Instigator (Doublestrike, if unblocked allows you to play 2 goblins for free), Quest for the Goblin Lord (Pumps all your goblins)

I hope I was able to help
Greetings
Muktol

I use 12 spot- removal spells for myself, and sideboarded are 4 mass- removals. But my vampires rely heavy on damaging the opponent to get stronger...they are red vampires and want to drink blood ;)
You could also try "Gatekeeper of Malakir" a cc3 (3 black) removal on 2 legs.

I personaly like decks that can switch between mill and self mill ;)

I would try to remove "Alchemist's Apprentice" and "Civilized Scholar" as the advantage you get from those cards is to small. One chumpblock that draws you a card for cc2 and a 0/1 for cc3 that draws you one card/turn.
Remove "Cerulean Wisps" (cc1 for 1 card is Ok, but there are better spells), "Dampen Thought" (Not enough arcane spells for that), "Divination" (To expensive to play)

With the free slots I would fill up "Dream Twist", "Inaction Injunction" (Depens on your opponens, perhaps 2 more into your sideboard) and "Thought Scour"

Some more suggestions from my mono-U mill deck (http://www.mtgvault.com/muktol/decks/monou-mill/) and my U/B control deck (http://www.mtgvault.com/muktol/decks/bu-control-discard/)
Draw/Discard:
Rushing-Tide Zubera...if it dies and got more than 3 (Blocking a 4/x) )damage, you can draw 3 cards
Visions of Beyond...cc1, Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead
Careful Consideration...cc4 draw 4 discard 4 or 2 (Depens if it is your turn or your opponents turn)
Compulsive Research...cc3, draw 3, discard 2 or 1 (2 cards or 1 land)

Mill:
Hedron Crab...cc1 0/2 defender that mills with landfall (3/land)
Sanity Grinding...cc3, really good in decks with high U-costs in it's cards

Defender
Kaijin of the Vanishing Touch...bounces back your opponents creatures so that he has to cast them again.

I hope I was able to help you
Greetings
Muktol

Your deck lacks some of the best and aggresive vampires there are. Furthermore I would remove some of the one-offs and put some other cards into your sideboard

Decide if either "Blood Seeker", "Blood Artist" or "Falkenrath Noble"... you can use one of the other in your sideboard. remove the rest
"Bloodflow Connoisseur"...remove. Cc3 for a 1/1 and you even have to sacrifice creatures to make him stronger.
"Child of Night"...remove and fill up the ranks of "Vampire Nighthawk" and "Vampire Nocturnus"
"Chosen of Markov"...remove. 4/4 seems impressive, but without any avoidance there are better creatures
"Sengir Vampire"...remove. Too expensive and you allready have enough finisher
"Vampire Interloper"...remove. There are better vampires
"Cower in Fear"...sideboard. Against mass
"Grasp of Darkness"...good card, if enough creatures die, you can think of using "Tragic Slip"
"Murder"...remove. Too expensive
"Public Execution" seems very expensive to me. The Question is, do you want to save 6 mana and so nothing in your turn if your opponent can very ofteh play arround this card?
"Trumpet Blast"...if you want to keep it, change to "Vampiric Fury". Costs 1 mana less to play, and they even get first strike
"Barter in Blood"...remove. This also hit's you and there are better spells for that if you want to
I would either focus on point removal or on discard to control my opponent, but don't try to mix it. Also BB-maana could be a problem in early games.

SOme suggestions from my own B-R Vampire deck (http://www.mtgvault.com/muktol/decks/br-tribal-vampire/)
Bloodghast (cc2, that comes again (if died) with landfall), Bloodline Keeper (cc4, produces tokens, if enough vampires are on the field -> flip -> +2/+2 for all your vampires), Pulse Tracker (cc1, does the same job as "Vampire Lacerator" but without the drawback in life), Stromkirk Captain (1+/1+ and first strike for all your vampires), Stromkirk Noble (cc1, 1/1, unblockable by humans), Rakish Heir (Does the same as "Curse of Stalked Prey" but in creature form: +1/+1 marker for every creature that does damage on your opponent)
Go for the Throat, Lightning Bolt, Terminate, Dreadbore (Good, cheap, removals)

If you want to use duallands I would recomend these:
Blackcleave Cliffs, Dragonskull Summit, Graven Cairns
Most of the time you want to overrun your opponent so "Cathedral of War" should not be that usefull. Like "Stensia Bloodhall" it just gives colorless mana. The Bloodhall would be really good if you wouln't have to tap it.

I hope I was able to help you
Greetings
Muktol