JSTOR is a great library database for finding images, photographs, and artwork. Switch to JSTOR's image search to find them:
JSTOR is an interdisciplinary archive of over one thousand leading academic journals from the humanities, social sciences, and sciences, as well as select monographs and other materials valuable for academic work.
JSTOR is an interdisciplinary archive of over one thousand leading academic journals from the humanities, social sciences, and sciences, as well as select monographs and other materials valuable for academic work. It is full-text searchable and includes images. There are embargos of between 3-5 years for most journal titles. Journals are always included from volume 1, issue 1.
You can also consider searching YouTube for educational documentaries, TedTalks, etc.