As critical as I tend to be, I cant really find fault with this model. I mean it looks kind of basic, but that's really what I'd expect from a simpsons game. What ever program it is in that makes those faces black, select the black faces and flip them (there should be an option to do that somewhere in the poly edit menu).
I guess you need to make some more generic simpsons type characters. If it's gonna be a FPS you cant really spend the whole time shooting homers. If you made some simpsons style enemies (like a commando, or a cop or something) then you could get around copywrite easier as it would qualify more as a fan game.
Nice work though. I'd be interested to see it in game!