To all:
I am designing a movie theater for a customer. I used to make a light box (a complicated process), but now stumbled onto what are called LED light panels. You can get them as small as 4 x 3 inches (about 1/8 inch thick) from ImagiLux. I plan on using homemade dry transfers or decals on the front side and either blackout or put a design on the back side. A friend had Staples print a high quality design onto the clear foil used for presentations. He taped the edges around the panel.
The panels need a 24 volt DC power supply.
Joe