ARTstor logo. Retrieved from Wikimedia Commons
ARTSTOR Digital Library is a database that contains more than two million images of art, architecture, the humanities, the social sciences, the sciences, and photography which span various cultures and time periods.
An interdisciplinary research tool that allows you to search over 300 reference works simultaneously, including limiting to audio or visual materials.
Remember - It is your responsibility to make sure that images you find fall within the public domain. Always check an institution's 'Terms and Conditions' regarding image use.