I just asked this on Quora after realizing that the British Museum (or Library, not sure if they're different) released public domain images from books, like sketches on Flickr. I remember it being a big headline in the news, "British Library/Museum releases 1 million images into the public domain".
However, checking the British Museum website for things like ceramics, every image is released under CC BY-NC-SA (Non-Commercial, attribution only). This is hugely restrictive, you couldn't use these images for a book, for example. But they are such good references!
My question is if there is anything like the British Museum collection but that is in the public domain. Something that includes various artifacts of different kinds, such as coins, ceramics, paintings, carvings, tools, fabrics, clothings, etc. I would like to find these public domain resources so I can use them in creating textbook material without.