The National Gallery of Art has donated the museum's entire collection of 53,000 open-access images to Wikimedia Commons. All the images are the hi-res publication quality jpegs that the Gallery would send for print publication and are dedicated CC0.
A parallel project is underway to also donate the museum's basic art object collection data of 120K artworks to Wikidata. The first phase of that should be completed within the next two months.