Take the back of the shadowbox and hotglue some aluminum foil on the back for extra reflection.
Use a drill bit and drill at hole through the side of the frame to allow the connection for the light rope to be made.
Take your 12' of light rope and hotglue that to the aluminum foil in a spiral shape.
Now put the box back together. Place your print inside the box against the glass. Set Shadow box on top of back and close fastners
(Current online picture does not show print installed.)
Here are some pictures of the finished product with the marquee print installed. Thanks to volley from the AVSForum for the print.