Atraxa

Okay, I'll try to suggest a few removals and I have a whole bunch of additions. First, there are counters types that you may be overlooking (storage, experience, & energy). I've included some of these as well as other good cards.

Consider Removing:
Chorus of the Conclave (Useful, but really high mana cost)
Necroplasm (Kills your stuff too and you don't have that much graveyard return)
Orzhov Advokist (Permanently buffs enemies for temporary bonus to you)
Renegade Krasis (Your creatures often enter small and grow. Won't evolve as much. Better for Naya decks.)
Immortal Servitude (Decent, but your creatures have a wide range of costs, so not super good)
Asceticism (No explanation necessary.)

Consider Adding these --
Lands:
Gavony Township (You want this.)
Llanowar Reborn (Buffs creatures that can't buff themselves, like your commander.)
Novijen, Heart of Progress (Buffs creatures you play)
Oran-Rief, the Vastwood (Buffs creatures you play)
Mirrodin's Core (Storage counters)
Aether Hub (Energy counters)
Rustic Clachan (Mediocre, but offers buff or white mana)

Creatures:
Triskelavus (Colorless tokens that deal direct damage)
Triskelion (Colorless direct damage)
Daxos the Returned (Great enchantment creatures)
Meren of Clan Nel Toth (Free creatures from your graveyard)
Ezuri, Claw of Progress (Big buff each turn)
Ludevic's Test Subject (Cheap 13/13 + trample)
Fertilid (Land search)
Karlov of the Ghost Council (Exile stuff)
Bloodcrazed Hoplite (Debuffs enemies)
Carnifex Demon (Kills untargetable enemies)
Korozda Gorgon (Kills indestructible stuff)
Djinn of Wishes (Cast spells without paying mana cost)
Vastwood Hydra (Distribute counters when killed)
Lifeblood Hydra (Draw cards when killed)
Hooded Hydra (Tokens when killed)
Heroes' Bane (Exponential growth)
Warden of the First Tree (Grows like Figure of Destiny)
Jarad, Golgari Lich Lord (Flinging stuff)
Aeon Chronicler (Draw extra card each turn)
Fungal Behemoth (Buffs target creature each turn)
Benalish Commander (Soldier token each turn)
Azor's Elocutors (Dumb win)

Artifacts:
Lux Cannon (Destroys stuff)
Eternity Vessel (Reset life to higher amount each turn)
Brain in a Jar (Free spells or massive scrying)
Orochi Hatchery (Baby snakes! Lots and lots of baby snake.)
Clearwater Goblet (Lots of life gain)
Coalition Relic (Mana battery)
Everflowing Chalice (Mana battery)
Energy Chamber (Buff each turn)
Darksteel Reactor (Dumb win)
Whip of Erebos (Life gain & unearth)
Bow of Nylea (Deathtouch & utility)
Bident of Thassa (Card draw & annoyance)
Spear of Heliod (Passive buff and defense)

Equipment:
Banshee's Blade (Transferable buff)

Enchantments:
Archmage Ascension (Search for cards)
Beastmaster Ascension (Buffs creatures)
Bloodchief Ascension (Hurt enemies and gain life)
Gutter Grime (Slime tokens)
Energy Vortex (Pay X to make opponents pay X+1 or take X+1 damage on their turn.)
Consulate Surveillance (Protection from one target)
Legacy's Allure (Steal something for UU)

Instants:
Delay (Counter spell for 1+U)
Abzan Charm (Utility)
Bioshift (Surprise buff or debuff)

Sorceries:
Soul's Might (Doubles power of target creature)

I would drop the following:
Iceberg (3 for a colorless mana each turn isn't that great)
Armorcraft Judge (there are better ways to draw cards and this only triggers when it enters)
Cold-Eyed Selkie (there are better ways to draw cards, mostly useless against non-blue opponents)
Etched Oracle (there are better ways to draw cards, only useful every third turn)
Languish (kills your commander, would be better if you could give all creatures -3/-3, like Toxic Deluge)