You could make animated signs like the old school Neons
I've done this myself and it comes out well
You could just have lit up arcade characters you just have to separate the colours onto different plexi sheets like a stencil
I have done this a few times and did this in my car too (Hadn't wiped all the fingerprints off yet)
http://i7.photobucket.com/albums/y279/aussie_ninja/plexi/litlogo4.jpgYou just use a led strip to light up the plexi and you have separate colours I did blue and white but it works well for pieces going on top of each other and arcade or video game characters would work well.
A good one you could do is the Space Invaders monster just have white leds for the outline and then the red or yellow for the colour

I always wanted to make a full size plexi cabinet but used the led and engravings on the side to have it light up like proper side art and the control panel too
