Fantastic question. Yes, I absolutely do think we should and will see gimmicks in MMA. We do have good storylines. You can never beat a good old fashioned feud between 2 guys who hate eachother(on camera), like Shamrock/Ortiz.
Kimo was the first guy I ever saw in MMA come to the octagon all decorated. It was his first fight in the UFC against Royce Gracie at UFC 3. Kimo came out with a cloak over his head, all tatooed up with religious crap, and was carrying the cross on his back. His motto was "To spread the gospel of Jesus Christ throughout the world. Unfortunately he was the one who got crucified.
But regardless, it was nice to see.
We'll see more. Fedor has a good gimmick. He's the unstoppable cyborg, the ultimate killing machine, the Russian experiment. Well actually it's not really a gimmick but it still works!