The Metropolitan Museum of Art's entire collection of public domain art is now available under the Creative Commons Zero license. You can download any one of the more than 375,000 high-resolution images of famous artworks and use it however your heart desires.
The Met's Open Access policy allows unrestricted use of any of the images of its digitized artworks in the public domain. This means if you're a student or artist and want to remix some of the work by throwing it into a collage or video project, you don't have to worry about copyrights.
The Met isn't the first museum to do this, but it's one of the biggest for a privately held collection.