Oh, and a current example, if anyone is interested:
http://commons.wikimedia.org/wiki/Commons:Village_pump#Picture_upload_questi...
One of the big problems is finding out whether copyright was renewed, but I'm not sure if the artwork in question was ever published in the USA anyway. People miss nuances so easily. And how on Earth do you find out details of an artist called "David Barker"?
Carcharoth