You can read the copyright laws regarding art at the copyright website...
http://www.copyright.gov for the home page of copyright stuff, and
http://www.copyright.gov/circs/circ40.html#general for more specific visual
If you really want to know the answer, call someone at the copyright office
and ask them. They are pretty nice and very helpful.
PO Box 31338
Bellingham, WA 98228
360 398 9801 office
360 398 0450 home
360 383 0001 fax