Might I suggest Strionic Resonator so you can copy all your activated abilities. put 2 lands.. do 6 damage with omnath and any other fun activated abilities.

Hey man, I run my own Omnath and the deck has slowly become my most competitive build. If i could make some suggestions here they are:

First thing I want to say, cut the lands man. I cannot imagine having that many lands being useful. Sure you guarantee land drops but how many lands can you play a turn? One. Most of time they will be dead cards until your next turn. My build seems to strive with the count I have, which is 36. I know that is low but the deck is meant to ramp. Maybe do not drop to 36 but 38-40 should be fine.

Other things to cut:

Ondu Giant

Just to slow of ramp card. Sure it is a body but you can find cheaper bodies that do the same exact thing. I ran him in my build and often times I found him to be way to slow.

Quirion Trailblazer and Silverglade Elemental

Same reason as above. I've never played them though so I don't know if they truly are dead cards. Silverglade Elemental is an Elemental so he has that bonus, but he is only a 4/4 and you lack a a sufficient amount of sac outlets to make that relevant.

Now possible additions:

Goblin Bombardment

This is one of the best cards in the deck, in my opinion. Instant speed removal. Make a boat load of tokens, someone tries to kill Omnath and just sac all the tokens and omnath for four damage. This card has so many advantages in this deck.

Momentous Fall, Life's Legacy, Greater Good, Drumhunter, Garruk's Packleader, Kavu Lair, Fruit of the First Tree, and Elemental Bond

One of Red and Green's biggest weakness is the lack of card draw it has. These cards work so well with Omnath that you might think you have blue.

Rite of the Raging Storm

This card works so well with our commander and the cards in the deck. It makes an elemental, it has a power of 5, triggering things like Warstorm Surge and Where Ancients Tread, and other people can use it to weaken our opponents.

Primal Growth, Nissa's Renewal, Skyshroud Claim, and Verdant Confluence

These ramp cards are just value. Between Skyshroud Claim and Primal Growth putting untap lands on the field, Verdant Confluence has so much utility, either being 3 lands or ramp and recursion, and Nissa's Renewal is just a decent amount of lands.

Good luck with your build. Hope you find Omnath as enjoyable as I do. If you want more ideas feel free to take a look at my deck, here is a link:

http://tappedout.net/mtg-decks/omnath-locus-of-spellslingin/

With Oracle of Mul Daya, he can actually play any amount of lands that he comes across in his deck, Aggro-Blaster.

I also recommend Courser of Kruphix for the same reason.