I use a great program for creating photos that use the thickness of the printed plastic to create the images. These are called lithophanes. Owen Ransen has done a great job of providing a multitude of objects that you can embed photos into. Once I have the necessary posts I'll provide a link but you should be able to find it by googling the program name which is PhotoToMesh. Output is in STL format. Matter control finds the files it creates too complicated but I downloaded CuraForRobo and it will slice and sve the files to an SD card. That works. When I get the time I will post some examples of lithophanes.