An alternative to using copyrighted material is using works available through Creative Commons. Creative Commons is a non-profit organization that allows creators to share their works, often under certain conditions. Creative Commons provides six different licenses that provide various levels of permissions on the use and copying of works. The Creative Commons website explains what type of conditions are applied to the work by the different licenses. Information on Creative Commons can be found in the Creative Commons Resources box to the right.
If using photographic material, major sites such as Google Images and Flickr have advanced searches that allow you to limit your search terms to items with Creative Commons licenses. The Canvas LMS also has the capability of finding images on Flickr Creative Commons when inserting an image on a page.