The J. Paul Getty Collection Website
You can access the collection here: http://www.getty.edu/art/collection/
The Getty offers the imagery to which it owns the rights without a fee. Its rights and permission statement can be found here: https://www.getty.edu/about/whatwedo/opencontent.html
You can search the collection here: https://search.getty.edu/gateway/search?q=&cat=highlight&f=%22Open+Content+Images%22&rows=10&srt=a&dir=s&pg=1
The J. Paul Getty Collection offers a rich archive of material, including artworks, photographs, historic documents, and other materials for digital download copyright free. The website states that “Currently, there are over 100,000 images from the J. Paul Getty Museum and the Getty Research Institute available through its Open Content Program. Other images include paintings, drawings, manuscripts, photographs, antiquities, sculpture, decorative arts, artists’ sketchbooks, watercolors, rare prints from the 16th through the 18th century, and 19th-century architectural drawings of cultural landmarks.” The Getty gives open access to images that it believes are out of copyright, but ultimately it is up to the individual user to determine rights. It also supports fair use of its imagery. If an image is used, the museum requests that credit be given to its Open Content Program, and that a copy of any publication be offered free of charge to the collection.