Instead of paying the full mana cost, you could put a lot of cards in your graveyard (which many competitive decks tend to do) and pay the minimal cost for each of them
Apart from the other toughness-matters commanders, Doran, the Siege Tower fits in treefolk typal decks alongside cards like Fangorn, Tree Shepherd
All are very good, except one for being, in my view, very conditional and heavy: Voice of Many
Speaking of just big and demony, Desecration Demon is quite a lot of card for the mana and not the kind of drawback that will wreak you, just one that leads to a bit of a dead do nothing card too much of the time for this to be all that good
2 Set Sail for a More Casual Adventure
This combat-based strategy needs some muscle to back it up, so cards like Quietus Spike see play, though make sure that you dont equip a ninja you plan on returning to your hand