The idea of a lithophane from the photograph is a sound one. It reduces a good number of uncertainties to nearly zero. Using a white or translucent filament and a high contrast photo will give you good results. Another aspect of a lithophane is the novelty of the invisible image appearing from the print. I suspect with the right lighting the lithophane might appear as the positive of the paw, rather than the depression of the cast.

The overall size is still a factor, although you may get sufficient detail from a lithophane if the settings are tight. In what dimensions are you working?