I'd recommend you build this on MTGO. Seems fun, but boy is it a lot of clerical work!

Bioshift would be sick in here! I like it a lot +1 from me.

I considered it, but it's a one-to-one transfer and is single-shot, so couldn't find a good slot for it.

No Vigor ?

For a good commander control, in my decks that run counters try Krasis Incubation

For some draw when you need it try Give / Take

Llanowar Reborn can help to get that extra counter on someone when you need it.

Cauldron of Souls can make your creatures really hard to take of. Since the +1/+1 and -1/-1 just cancel each other out.

Opal Palace ??

I like Vigor , but the GGG in it's cost makes it difficult to pop out early, and by the time I do, there's usually other options that can overwhelm by pure numbers.

Llanowar Reborn and Give / Take are a good fit, thanks! :-)

I hadn't thought of Cauldron of Souls ; I'm going to have to find a slot for that, it's too good not to include.

Opal Palace can summon Jenara, Asura of War on turn four instead of three with an extra counter on her... but she can already make her own counters. I'm not sure it's really a good tradeoff for even a basic forest.

Thanks for the tips, guys, keep them coming!

Just checked rulings on the persist keyword: token creatures are still out of the game when they die and have persist. Not quite as good as I was hoping.

no Intangible Virtue to grant all your tokens bonuses? +1/+1 and vigilance can make a huge difference

I like it. I have a similar UG deck that has more bounce than tokens.

Thoughts:
Forgotten Ancient
Prime Speaker Zegana
Thrummingbird

and the top two picks
Budoka Gardener - early ramp, and then pretty much the biggest tokens around
Proteus Staff - insanely good in this - tuck problem creatures for defense, turn tokens into real creatures, turn ETB creatures into new creatures, stop people from wanting to play their general, etc...

cool deck, I only count 4 flyers so I would suggest Wonder or Sapphire Drake . A Simic Guildmage would be fun to bounce those +1/+1's around as needed.

If you're running GSZ, I'd suggest Dryad Arbor in place of a basic Forest. Turns the already useful tutor card into turn 1 ramp as well.

Hmm, that's good, might as well... Just seems like a waste of a tutor though.

Twilight Drover could be good in general. what about Wargate , Green Sun's Zenith , Chord of Calling , Worldly Tutor , or Congregation at Dawn to find stuff? Eldrazi Monument can help alot to prevent board wipes from wrecking you. Illusionist's Bracers , Rings of Brighthearth and Strionic Resonator could all have interesting interactions with the stuff this deck does. Oran-Rief, the Vastwood could be another source of +1/+1 counters to give new stuff a little more umph. Glare of Subdual could add some useful control elements. Slate of Ancestry , Skullclamp , and Fecundity can all add some draw. Druids' Repository , Citanul Hierophants , and Nature's Will can allow you to get mana off of creatures reliably, and Ashnod's Altar or Phyrexian Altar could let you get mana by sacrificing. Reveillark and Creeping Renaissance could let you recover from a wipe. Hornet Queen , Reach of Branches , Carrion Call and Gilt-Leaf Ambush can all be great sources of blockers.

you have my thanks for building a jenara deck that isn't voltron.

Thanks for all the suggestions! I have a lot of trimming I've got to do of the Maybeboard now!

I think it would be fun to copy Precursor Golem with Progenitor Mimic .

Then Rite of Replication !

O.O All the golems...

I dunno, Progenitor Mimic + Mycoloth is a personal favorite of mine, since each one can munch the tokens of it's predecessors and exponentially ramp the size of your army. :-)

Totally agree with shaistyone, you can't forget the Thrummingbird in a deck like this one, plus, Prime Speaker Zegana is really a good draw.

i don't like the complete absence of ramp, counterspells and removals. how do you plan to stop the opponents?

ascanio, Do you have any suggestions on things that would work well and not dilute the deck too much? Commander is a rough format for that, given the number of them you have to load your deck up with just to have some chance of drawing them, so I tend to just focus on out-pacing opponents instead.

you should first choose if you want your build to be more control or aggro. if you go with aggro, pack a lot of ramp and some cheap removal like Path to Exile , if you want more control go with counterspell and even more white removals. for both you need more card draw, even counters related cards like Zegana or Sage of Fables