It is seemingly a "new" thing. Same as not depicting any living creature is also forbidden. There are many examples of Renaisance era Muslim glass & mosaic depictions & sculptures of birds, animals, and even people just in the Corning Museum of Glass.
Also, check this:
Mohammed at Medina, from an Arab or central Asian medieval-era manuscript.
Here is an interesting archive of Mohammad images throughout history.
Or, for something modern, try this:
Steve D., the proprietor of this blog , fashioned his own statement about the controversy by Photoshopping one of the Jyllands-Posten drawings onto the rear end of a camel.
