Light-boxes are a very common way of doing outdoor signage. Sizes can range from small 300mm wide or high, this is the suit standard light tubing or go as large as your imagination and budget needs to go. Panels can be made from acrylic, polycarbonate or flex-face materials. This allows graphics from simple one colour to full colour to be illuminated.
Back-lit or slim-light light boxes are getting as thin as 10mm. Slim light-boxes are great for internal and external uses when graphics are regularly changed and they have a great up-market look and feel.