I'll use my current rear license plate frame (HORN BROKE, WATCH FOR FINGER) and the front frame (SPORT CHALET -- I'D RATHER BE SKIING) but those aren't really all that visible. Neither are bumper stickers, although I have some more "Linux, where do you want to go today?" stickers. I'd rather have a real color (candy-apple orange by choice!), but this is SoCal and we have a lot of sun :-(
Never got that good :-)