5meter LED strip $8 eBay
11x14 Shadow Box, $10 Michaels (for 2 right now)
11x14 Opaque Acrylic cut about $5-8
12V 500ma wall Plug. ($2-5)
misc parts and tools.
Wire (old phone cord) free or local 99cents only store.
Power Switch Optional $1 All Electronics.
Power Socket Option $0.50 All Electronics.
Heat Shrink Tubing.
So this project is pretty self explanatory.
Disassemble the shadow box.
Cut the LED strips to the length of the back piece making sure to cut in the center of the copper solder joints.
Remove the tape backing from the light strips and apply to the shadow box back piece.
Use an exacto-knife to remove the clear rubber to gain access to the copper solder pads.
Solder wires from one strip to the next in whatever configuration works for you, test polarity to make sure you get it right as you go.
Solder 12V wall plug to LED wiring, ensuring proper polarity. Use heat shrink tubing to cover solder connections.
Suggestion, spray paint the back piece white and allow to dry before sticking down LED strips.
Trying different diffusing methods to get rid of light/dark lines.