As you can see in the photo above, the 2D image has been rendered in a thin 3D form. The print media is not completely opaque and thus light can leak through from behind, with more light coming through the thinnest areas. This creates what Shapeways terms a "light sculpture" . We think it's a pretty cool way to use 3D print tech.
Don't limit yourself to photographs, either. Shapeways accepts images, which could include abstract and computer generated scenes. Text would also be straightforward to use.
Pricing, as always, depends on how big an object you'll be producing, but we believe it to be in the USD$40-60 range. And don't forget to order one of those fancy stands to hold up your light sculpture!