Seedborn Muse so you can add to your mana pool on each of your opponents turns??

Your deck looks pretty good. When I play my deck, Omnificent Omnath, I usually run into quite a few flying creatures, which can be devastating for me. I would suggest a little more token spam such as Avenger of Zendikar , Howl of the Night Pack , and Beacon of Creation , then playing something like Spidersilk Armor . Makes for some great chum blockers. Or if you want something with a little more offense, Hurricane and Tornado Elemental are great. +1

why Prismatic Omen ?

and no Primordial Hydra ?

for ramp Mana Reflection could be good...

I mean, Blade of Selves is an auto-include, right?

switch out omnath as your commander?

Are you exploiting Kamahl's ability to turn opponent's land into mana at all?

You have an Extraplanar Lens in the deck, so consider swapping out all of your forests for Snow-Covered Forests, makes it less likely for your opponents to also benefit from the lens.

Triumph of the Hordes

I would replace Nullmage Shepherd with Glissa Sunseeker, Both are better in their own scenarios, but I think Glissa comes out on top most of the time. She is not reliant upon having multiple creatures, the downside is Nullmage Shepherd can tap 8 creatures to destroy two targets at once. And it can hit enchantments while Glissa cannot.

I know this is late but what about all mana dorks, Genesis Wave , Primal Surge , and protection like Eldrazi Monument

Have you considered Baru, Fist of Krosa ? He gives a mini-overrun whenever a forest enters, which would presumably be rather often, especially with Azusa and friends.