Creative Commons offers a search tool to find media which can be used under a CC license. This tool links to search services that provide options for finding works that you are able to use.
Advanced options in Google Search allow you to filter results by "usage rights." This means that you can use a Google search to find media works or text that the creator has given permission to use.
Wikimedia Commons is a free-content website which sorts media works into the categories of "Images," "Sounds," and Videos. You can search for media that you have permission to use and upload your own works to share with others.
Schongauer, Martin, 15th cent. (c.1480-90). Series of Coats of Arms: Shield with a Greyhound, Held by a Wild Man. Retrieved from ARTstor.