The unfortunate and somewhat comical side effect of having fully inserted a purple wax crayon up my nose (for kicks) as a child, my brain is incapable of learning certain things. Specifically, things having to do with bicycle modding trends. I know that people do it. I've seen'em around. I... just don't know anything about it.
I have eyes, though, and I can tell you this. These bicycle spinners from Deuce-Usa will give you one sweet set of pimpin wheels. Integrating "the world's first patented hub spinner technology", they'll fit all 20-inch wheels and "depending on the speed that you are riding your bike, they spin for a minimum of a half a minute or more after you stop".
They'll carve a nice little hole in your wallet too, at $220 for one. -DP