"A lithophane is an etched or molded artwork in very thin translucent porcelain or plastic that can only be seen clearly when back lit with a light source."  Wikipedia

Lithophane - source image
Original image
Lithophane - regular light
3D print with regular light
Lithophane - back lit
3D print back lit

How to create and 3D print a lithophane

- Print time can be very long... especially if your image is large and has many dark portions. Try selecting images on a light background, or use the mask and bgrd editor to remove the background.
- Do not modify the model height in your slicer... Always keep it at 2 mm.