Hmmm For some reason, every time I read this thread, my mind was saying 'back lit' wall art. That would be cool!

So, you're essentially looking for decals that will glow in black light....
I don't know anything about this, but did a quick search, thinking you could find sheets of paper, ready for blacklight, that could be cut and used, if you're crafty. I didn't find that, but did see that there are blacklight paints available. Then, I found something pretty interesting on the following webpage;
http://childrens-parties.suite101.com/article.cfm/an_outer_space_astronaut_partyTo give the party room the feel of the Milky Way, use black light bulbs in all of the lamps and light fixtures. Use laundry detergent to paint stars, planets and meteoroids onto the walls of the room. (Everything with the laundry detergent on it will glow.) In the middle of the room, hang a planet piņata. Make the piņata yourself by use paper mache and paint to create Mars, Jupiter or whichever planet the birthday boy chooses.Now, I don't know if the type of detergent matters, or it if would be uniform in appearance, if it would warp the material, etc. but I guess it could be worth an experiment?
Also, I'd suggest not 'splattering' the walls with it. That might be misinterpreted by some.
