I had never heard of "lithophanes" before seeing them here on Thingiverse. Having found them, and having printed several myself, these things are amazing! This is my contribution to this awesome art form - Saint Michael the Archangel as painted by Guido Reni (I believe).
-=[ UPDATE ]=- So, ummmmm.... yeah... It seems I accidentally created these with the image settings set to "negative." I have uploaded the corrected version (as _v2). Anyone care to tell me why there would be a "negative" setting on a lithophane creator?!
How I Designed This This was rendered via the 3dp.rocks/lithophane web site. _v2 was rendered directly in Cura 2.5