The Paul J. Getty Museum announces their new 'Open Content' Program. All of the Getty's public domain objects, totalling around 4,600, are available for download as high-resolution images and are free to use, modify, and publish for any purpose. They will be releasing more images over time. You can browse the images currently available from this link. You may read more about their program here.
Update 11/10/2013: The Getty Open Content Program now has around 10,000 images available for unrestricted use.
