One of the best ways to find images with creative common licenses is to use Google to search. Do a regular Google image search, then click on tools, then select Creative Commons licensing.

This is one of the best ways to find free images, including from Unsplash, Pixabay, and Pexels. The Google search will also show you images with Creative Commons licenses available on Wikimedia Commons and on my next favorite image source: Flickr.

If you aren't yet searching for Flickr images with Creative Commons licenses, you are in for a fantastic surprise. Probably shouldn't even mention it because it's a pretty well-kept secret, but there you go.

Caution: just because a Google image search says an image is licenseable under Creative Commons doesn't mean it actually is. You have to check.