Hyperallergic reports: Art Institute of Chicago Offers Thousands of Free, High-Resolution Images. That would be unrestricted access to thousands of images — exactly 44,313, with more to be added — under the Creative Commons Zero (CC0) license. “This move is not unprecedented. According to Artnet News, the Metropolitan Museum of Art also made all of the public domain works in its collection available online back in February 2017.”
Here are the images from the Hyperallergic announcement.
Van Gogh, Munch
Monet, ancient Egyptian