Muktol

Personally I would sideboard [[Naturalize]], normally you don't have to deal with artifacts/ enchantments in every match. [[Hydra's Growth]] sounds like overkill to me, especially when you have [[Assault Formation]] on the battlefield. A single [[Wall of Denial]] will need 3 turns to defeat an opponent, while [[Hover Barrier]] needs four, so [[Hydra's Growth]] will make nearly no difference.
I would also replace [[Rolling Stones]] with [[Arcades, the Strategist]] or [[High Alert]] as they not only allow your creatures to attack but also bring the toughness-bonus of [[Assault Formation]] to bear.

Further suggestions:
[[Axebane Guardian]]...not as tough, but can serve as mana-fixer. Tough you may want to add a mana-sink to use the mana produced with him. [[Overgrown Battlement]] would be another variant, quicker, variant tough it only produces green mana.
[[Order of the Stars]]... one of my favourite defenders, not real tough, but hard to deal with.
[[Stalwart Shield-Bearers]]...again, not really one of the toughest defenders, but gives all your other defenders +0/+2
[[Drift of Phantasms]]...can help you to get cmc3 mana cards in your hands.
[[Seaside Citadel]]...to solve mana-problems.
[[Indomitable Ancients]], [[Bar the Door]], [[Slagwurm Armor]], [[Wall of Reverence]], [[Wall of Shards]], [[Favorable Winds]]

A short deck- and how-to-play description would be a nice addition. If you don't know what to write, you might find some ideas here:
https://www.mtgvault.com/muktol/decks/why-you-should-add-description/
[[Ram Through]] instead of [[Prey Upon]]. Personally I would remove {{Fog]] and add something like [[Aspect of Hydra]] or similar cards.

I didn't see [[Wrangle]] as a way to untap things, but more as control-option. If you want something to untap other things. without the versatility of [[Wrangle]], then you could take a look at [[Magewright's Stone]] or [[Thornbite Staff]]. The Staff has a nice synergy with dying creatures, and if you throw in e.g. [[Skirk Prospector]] you can do an combo, but it's also more expensive to play (3 Mana Stone vs. 6 Mana Staff)

Personally I would trade [[Goblin Warchief]] for [[Goblin Chieftain]] as I think you will profit more from the +1/+1 than from the lower cmc. Also [[Goblin Tunneler]] (or [[Break Through the Line]], due to the haste-ability) instead of [[Sneaking Guide]].
It would be interesting how well [[Conspicuous Snoop]] really works. Could you write a short comment after you have done some testgames?

[[Signal Pest]], [[Larger Than Life]], ([[Wild Defiance]]) could be ideas, and I would lower the numbr of Forests by 1-2

Depends on how you want to achieve victory here. It looks like the beginning of a goblin-swarm deck, but with all those 2-off's it will be hard to get a continuous performance.
[[Conspicuous Snoop]] is a strong card, but it only works with [[Krenko, Mob Boss]] and [[Sneaking Guide]] and the chances of getting those atop of your library while you have this little fellow out are slim.
I would also try to get the deck modern-legal.

If you want to play a little more aggressive [[Rat Colony]] and [[Swarm of Rats]] could be useful.
[[Typhoid Rats]] can serve as indirect removal, while [[Doom Blade]] can take the direct treats your opponent puts on the field.
Last [[Bad Moon]] could be used to strengthen all your rats a little more.

Am I this predictable?

[[Thraben Doomsayer]] could be used instead of [[Gather the Townsfolk]] if you want a more constant token production.
Another card I can recommend would be [[Student of Warfare]], tough he's expensive to level up.

A short deck- and how to play description would be fine, even if there is a youtube link. Some of us still prefer to read, instead of watching a video ;)
Drawback on [[Indomitable Ancient]] is that it's not standard-legal.

Personally I would trade [[Metallic Mimic]] for [[Corsair Captain]]. The captain has the advantage of strengthening all creatures, not only the ones who enter after him.

I would rather try to find mechanics (Fear, Intimidate and so on.) that are underrated, but even this will be hard.

Yes, but that should only be relevant if your opponent has more creatures than you (e.g. Elves or Goblins)

In my opinion it's hard to rate a card in general as many cards only show their full potential in combination with others, but do very few on their own. So to me, except for [[Ashiok, Dream Render]] (which I've seen in some MTGA sideboards while I was active there), the cards you've listed until are underrated/ overpowered only for 1-2 decks, but others would never even think of adding them.
For example [[Ancient Greenwarden]] works very well in a standard landfall deck, but would ultimately loose in modern to [[Crucible of Worlds]] because it's faster to play and can be used by more decks. Another example would be [[Midnight Guard]] which is a creature with pseudo vigilance, but in combination with [[Presence of Gond]] he reaches a whole new level.

I know it doesn't fit the colour scheme perfectly, and it's ability is rather expensive in comparison to [[Steel Overseer]], but what about [[Gavony Township]]?

Sadly [[Artful Dodge]] is blue, because it would fit in here perfectly. [[Nightbird's Clutches]] would be a red alternative, tough it only affects 2 creatures and the flashback is rather expensive.

What about [[Mirrorweave]] to turn all those tokens you create into [[Seven Dwarves]] before you attack? Would be kind of an overkill, but it would fit the "Mirror" theme of the deck.

A short deck and how-to-play description would be a nice addition.
Personally I think 8 changelings should be enough to activate the abilitys of your party people and thus would remove [[Stonework Packbeast]] to add some equipment to give your creatures either evasion or some additional punch: [[Cobbled Wings]], [[Horned Helm]] or [[Bonesplitter]] would be my "standard" choices in pauper.

Why not use the confusion part to your advantage? Personally I would build (/play) this as a blue artifact deck, which has [[Arcane Adaptation]] + [[Liliana's Contract]] as surprise win-con. Use your creatures to ramp, draw and search for your key-components, or have them as protective barrier around you that replace themself with tokens.

Against boardswipers you could use [[Hissing Iguanar]], at least in the sideboard.
To get rid of your colour problem 2 basic forests and plains, and some searchlands like [[Evolving Wilds]] might be an idea.
Personally I would favour [[Goblin Gathering]] over [[Dragon Fodder]] or [[Krenko's Command]], because it gets stronger the more you play it. I would also include some carddraw, e.g. [Tormenting Voice]], to make sure you draw enough cards, as low CMC decks tend to run out of handcards (and thus options) rather fast. Last, [[Goblin Grenade]] is pauper legal, so if you're looking for a cheap, strong, additional, finisher, this might be an idea.