well this is a controversial subject and I know I will get blasted for it but I use regular print media. or vinyl, light shows trough it just fine, you would want to use a vinyl with clear adhesive, depending on the graphic some times the gray glue can look blotchy when back lit, I have also used translucent print media this works well and is made for this application....and it is easy to use you do not need to double print it... I guess it depends on what type of effect you want
//chopper