This is the output from a new tool I'm writing, you drop images on your STL files to texture the surface. It all works in the GPU and you can see the changes you make in real time. STL generation takes about 200mS and you can apply multiple textures over each other for various effects.
These are quite big models, and may be difficult to print.

I have some tidying up to do, but an Alpha version will be available to try out on the Lithophane site in the next week or two.

For those who have been waiting, sorry for the delay, I had to earn some money :)