Thought I would weigh in on this...... I seem to think differently than most people who have replied.
I have powdercoated white rims on my metallic blue SHO, I think it looks great. When I told people my idea for the paint scheme and the white rims everyone said it would look dumb. However, after I got it done people were like "Damn that looks good." I get stopped by people all the time that tell me they love the color of the car with the rims. So if you don't like em, I guess maybe you havent seen the right combination yet. Or maybe you just have different taste. That being said, I personally think that gun-metal or black rims (especially flat black) are the most disgusting looking thing I have ever seen. I have seen a few (very few) cars with black rims that looked good, however the rims always have the polished lip. So I would say if you have the black, you have to have the polished lip. But like I said before, maybe I have only seen p.o.s. cars here that make the rims look bad or perhaps I just have a different taste. I dont think any colors besides black or white would look good though. I mean they might look so-so, but would probably look better with the black/polished lip, white, or chrome/polish.