The Getty Museum released on 14th-August-2013 over 4,000 images into public domain (i.e. free). According to the ArtObserved article on the museum’s public release made public on their Getty Iris blog, this is part of their, “Open Content” commitment of their digital resources.
You can search these images using: Getty Search Gateway .
Stanczyk, knows what you’re thinking, “I am too busy on my genealogy to search through museum images”. But I politely urge you to reconsider. While I was searching their images, I found a genealogical family tree, of Duke Ludwig I of Brzeg (amongst many other images he commissioned). A Polish noble of house Piast. So if your family tree intersects, get thee to the Getty Museum. For those curious, I have posted the images to this blog. The text is Fraktur looking, gothic, German script.