Another big name is Bill Conti. I'd love to listen to his take on Iron Man.
Schifrin wouldn't be a bad choice, either, although he did compose one of the more unnerving Paramount Television fanfares .
From Favreau's comments at Comic Con, I think this movie is going more for heavy metal than Jazzy kind of tunes.
God I hope that he doesn't put the newest Linkin Park/Evanesence/metal song in the movie. I want a classic movie that when I watch years later, I won't hear some song that will really date it.