I've never been a fan of tribal graphics, and I don't think they fit the car too well. Could you post up the original picture of the car? I might have a couple ideas I could work with to go with a "clean/mean" look.
It may sound dumb, but if you have access to a copy of need for speed underground 1 or 2, grab a 240sx or something and try out the graphics in there. They have about any type of graphic in that game.