CLKER - Free clip art you can use for anything you like

Pics 4 Learning - A curated image library that is safe and free for education. Teachers and students can use the copyright-friendly photos and illustrations for classroom projects, web sites, videos, portfolios, or any other projects in an educational setting.

Google Images - Search the internet for photos, clipart, etc.  Some images will be copyrighted and not free for use.  To limit the search for images free to use: 1) search for the image, 2) Click on "Tools" at the top of the page, 3) click on "Usage Rights" and choose "Creative Commons licenses".  The images that remain are free to use at no cost; some may require attribution for use on public sites.

Help Desk Geek - 15 Best Websites for Free Clipart Downloads.  Some of the art is not free and some are free but require attribution.  See each website to determine the status of the images on that site.