Corpsejack Menace, Kalonian Hydra, Primordial Hydra, Hardened Scales, Hangarback Walker, Doubling Season, Retribution of the Ancients, Oran-Rief, the Vastwood, Armory of Iroas, Bow of Nylea, Cathars' Crusade, High Sentinels of Arashin, Scute Mob, Vinelasher Kudzu, Elite Scaleguard... to name a few.

I would also recommend upping your creature count, 21 seems pretty low for Commander/EDH. If you don't know what to cut out, consider swapping instants/sorceries for permanents, like creatures, enchantments, artifacts and planeswalkers. For instance, if you replaced Dromoka's Gift with High Sentinels of Arashin, your mana curve remains mostly unaffected, and you now have the potential to distribute far more than just 4 +1/+1 counters, all with just one card.

Okay, I see what you are getting at. Is Daghatar the Adamant doing the job for this deck's purpose?

looks useful to me, but playing the deck will tell you for sure. With cards like Abzan Falconer and Abzan Battle Priest, the theory seems viable, at least.

However, his ability to move counters would synergize really well with cards like Corpsejack Menace and Hardened Scales, because "moving" counters is the same as "placing" them. (Also, entering with counters means those counters get doubled by cards like corpsejack and Doubling Season.) Anyway, with Daghatar the Adamant & Hardened Scales on the field, you could one counter into 2 counters, and then with a card like corpsejack on the field, you could THEN double those counters.

That sounds nice. I like the cards like Abzan Falconer with this kind of deck because if you get the perfect hand then you have it set up perfectly.

lol, perfection is perfect. =P

Also, consider dropping Arrow Volley Trap and replacing it with Feat of Resistance (one of my favorite cards).

Also also, as for your commander, I would (ideally) try to keep about 6 or seven counters on him, that way he's threatening a win by Commander-damage in four turns or less. But I would also keep putting more counters on him, and then pumping up other creatures by moving them, but never let him get too low. That way, he is harder to remove by damage. Additionally, I would use white's "protection" spells or artifact hexproof to keep him safe. That's my first impression, but playtesting might change that strategy over time, too.

I personally have two decks based around +1/+1 counters, because they are a fun, explosive strategy. An abzan modern deck (Bolster a Corpsejack Menace to Society...) and a naya edh (Naya'll Feel Marath), which you could look at for inspiration (I use a LOT of green cards you might like, too many to list here, lol, plus some good white ones in the EDH deck).

Oh yeah! Also also also, Wall of Limbs might be fun, too.

Alright thanks man for the suggestions.