Open Access Images
The following sites maintain good lists of musuems, galleries, etc. that provide images with open licenses or in the public domain.
- Open access image libraries – a list | Apollo Magazine
- High Quality Collections of Digitized Art and Archival Finds | simon sarris
The next resources seems to be meta-collections of open access images.
- Medium: Images – Collections – The Public Domain Review
- Public Domain Free Creative Commons Images | rawpixel
This last resource is a custom Google search engine created by Austin Kleon that searches across many of resources provided by the first set of resources above.