I have stickers on my bike. I think they're worth showing / discussing:
"engrish" (silly things in English seen in Japan / China / etc.). I found this in a department store in Japan.
Detroit Derby Girls. I got this after taking my wife to see roller-derby, Detroit style (yes, they actually still do that - no, not quite like in the movie, but pretty close).
I want to add one more (specifically, I usually just acquire silly things spontaneously) - a Detroit Red Wings winged wheel for the opposite side of the down-tube.