Last year at a ceramic educators conference, a guy did an interesting demo. He used a d!git*l cam to make it quick and easy, but basically he printed on a coated paper used to make decals. The printer was some ancient beast that he guards zealously; it uses a toner that contains some form of iron (probably as an oxide). Apparently most of today's printers do not use the magic ingredient.
Once printed, the decal is dunked in water and slid onto a ceramic object. For his purposes he used a plate that had already been fired with a white ceramic glaze. With the decal in place, the piece would be fired again. The transparent decal film burns away, and in this case, the iron component appeared as a sepia-like tone. Probably a more common technique is to create silk screens and make your own screen ink using the powdered minerals, eye-of-newt and bat wings commonly used to create glazes. Even what are considered relatively low firing temperatures will burn off most organic stuff.
There is probably a way to use a half-toned screened image and a rubber blanket to offset print a photographic image onto ceramic also.
DaveT (who plays with ceramics a bit, but hasn't tried photos)