Do you have anything specific in mind? Forums Thread for which section? Cool sigs, there are quite a few talented people here.
I would suggest you look through some of the artist's work here and pick out which one could do what you want best. but that's just me of course.
//OT - If you toss a few ideas up I might be able to help... although I'm definitely no where close to being good compared to some of the other people around here. >_<