Do you want a Dumbo cake pan? I've never seen one.
For my daughter's Dumbo cake I drew a picture of him onto a plain sheet cake, and filled in with some grey icing. I gently tap in an outline using a tooth pick, then play connect the dots with a thin bead of black icing.
However, recently our local grocery's bakery started offering edible transfers made from a picture. For a few bucks, they'll transfer a photo or other picture onto an edible sheet of film via computer. I've never tasted them, but the images look pretty good.