Light up window signs

I was wondering if anyone has ever considered a "sign" in one of their back windows that lights up a little bit. I was thinking about this and thought that a better way would be to use a blacklight-style decal and then put a neon or LED light behind it and make it illuminate the decal.
I own a 1985 Buick Regal, the small rear window - would a Buick symbol in the window that lights up look alright or is this some crazy idea of mine?

Later.

That would be sweet. I bet you a light up sign would be illegal, but I bet if the vinyl reacted to blacklight, but another driver couldn't see the blacklight it wouldn't be illegal and you could get away with it. YEAAAHHHHHH!!!!!!! I say go for it.

Get one of those invisible marker pens for security marking stuff (meant to only show up in UV light) and a stencil. Draw your design on the window and put a UV neon behind it. I did this to my PC and it looks cool! :cool:

You will have to redo it every time you clean your back window, with some people that is ok because they never clean the windows.

The marker pens I was talking about are waterproof (they are for security tagging things - what good would they be if they washed off?).

You could always cover your design with clear film anyway.