The Getty Museum has begun scanning and placing their collection of artwork that is Public Domain online. That means there are a lot of neat pieces of art that may be used free without seeking permission from them to use it. They ask that you credit them for scanning it in your notes. I know a lot of individuals look for artwork for their stories here, so I thought I would share. You would definitely need to resize the images from their current size to use though (easy with Gimp or Photoshop). Anyway, here's the link to their press release, and a link to the gallery!