The shadow of this cube in different directions gives QR codes pointing to the Wikipedia articles for Kurt Godel, M.C. Escher, and J.S. Bach respectively. Also a pretty challenging print test. Note that QR codes cannot be read in mirror image, so only 3 of the 6 possible cube orientations cast a readable shadow.
Notes. This was generated using a reduced-url QR code generator, a paint program to connect disconnected sections, Inkscape to convert to dxf, and OpenScad to extrude, rotate, and intersect the 3 images. OpenScad rendering took almost 30 minutes on a fast computer.
QR codes are fortunately very forgiving of fairly large modifications due to their built-in parity and redundancy schemes, and I verified readability of the images up through the dxf stage. (Although I got pretty close to the limit on one image, and my camera QR scanner had to rescan a few times to get a read.)
This is a complex image. To get a readable shadow your light source will need to be pretty far away to get a flat pass through. Perhaps someday I'll do a version with transformed geometry, matching specific close-up point sources.
If you can't get it to print cleanly enough to read, hey, claim it's a Borg Cube and gift it to your Trekkie friends.
Best to print this in black; then you may be able to get a QR scanner read looking directly at faces rather than shadows.