Use these search engines to search multiple sites with OER resources:
(developed at SUNY Geneseo's Milne Library)
(developed by George Mason University Libraries)
Pixabay: "...copyright free images and videos. All contents are released under Creative Commons CC0, which makes them safe to use without asking for permission or giving credit to the artist"
openclipart: Drawings and clipart that are all in the public domain.
Creative Commons Search: Allows you to search different image and video sources using different CC criteria.
Pixnio: High quality public domain images that can be used freely for any personal or commercial use.