The key to making this look so awesome was the thin layer of styrene immediately over the top of the LEDs - providing a single, flat surface for the image to sit on top of.
A photo-quality print is lined up and fixed over the entire board using Photo Mount spray...
... and the excess trimmed off. The print on the surface is pale enough that the LEDs shine through the relatively lightweight (90gsm?) photo paper meaning no nasty cutouts or holes required in the image surface.
Instead of just stopping there, Steve went to the trouble of making a striking green frame for the image, complete with sliding on-off switch to stop the battery from draining too quickly.
With a 5v regulator onboard, the LEDs can be powered from a single PP3 9v battery.
Having mounted the image onto the uprights, a simple - but effective - acrylic border is placed around the outside of the photo and fixed in place with hot glue.
The final (amazing-looking) finished product. Hopefully we've done enough to help Justin earn a few brownie points for this one ;-)