A lithophane is a heightmap of whatever image you want displayed, and works be shining light through it from behind. Darker parts of the image are thicker, causing them to block more light and be darker.

Over the last couple of weeks I created a few versions of this light box trying to make it thinner and have the light spread more evenly. I'm on version 4 now and I'm pretty happy with it. I just need to create small indents inside the box to help me place the LED strips more accurately on future versions and larger ones. This one holds a 110x110 millimeter image, and I should be able to print a box for 220x220 millimeter images too. Swapping images in the lightbox just takes a few seconds using the slot on the bottom.

This particular lithophane is somewhat low quality with all that horizontal banding in the print but despite that it's still super cool looking in person. I believe this is just caused by the mediocre quality filament I used since lithophanes are quite sensitive to the diameter of the filament and need something extremely consistent to not have visible banding. I am currently printing another lithophane using my better filament to see if that will fix it. (edit: switching to a better quality filament fixed it.)

The art in this image is by   felisrandomis and is uploaded here!