I stopped attaching foreign objects in the vicinity of my bicycle wheels ever since I ruined a perfectly good Roy Campanella basball card a long time ago.
But let me pass along a couple of websites for wheel decorations suggested by a reader. Each sells circuit boards with LED lights attached that mount on the spokes of a bike wheel and display text or images as the wheel spins.
I've seen these before, but never really looked into it. If you have some time over the holidays, this might be a fun project, especially if you ride at night a lot.
Hokey Spokes have pre-selected images that can be displayed, or users can input a text message. If you're real handy, you might want to check out the SpokePOV. It's a kit that requires some soldering, but you can create your own images (like Homer, above), as well as text.
Picture from hokieznuts at flickr.com.
Thanks to Andy for the suggestion.