Yes, but how do you know the original image is out of copyright? It’s mostly obvious for older pieces, but for newer ones it’s not always obvious when an artist painted a work. Even with apparently older images, the worry is that the photo is actually of a reworking of an older piece that isn’t out of copyright.

This would be solved by linking each photo back to the originating gallery.

(I contribute to Standard Ebooks – https://standardebooks.org/ – and would like to use Artvee’s imagery for covers, but without a link back to the originating site to check for a CC0 grant it ends up being a trawl through Hathi looking for photographic proof that the image is out of copyright.)