Look for images online that grant a Creative Commons license (CC). "The Creative Commons copyright licenses and tools forge a balance inside the traditional “all rights reserved” setting that copyright law creates. Our tools give everyone from individual creators to large companies and institutions a simple, standardized way to grant copyright permissions to their creative work.." The permissions will vary by creator but one can often find images that allow free use with proper attribution.
"A reverse image search engine. It finds out where an image came from, how it is being used, if modified versions of the image exist, or if there is a higher resolution version." Can also be used to identify an image for which you have no information or to detect if an image was created by AI.