The databases on this page provide access to millions of images, including paintings, photographs, historical images, graphic art and much, much more. See Get Started with ARTstor for a quick tutorial on using that resource to view, present and manage images.
"Wikimedia Commons is a media file repository making available public domain and freely-licensed educational media content (images, sound and video clips) to everyone..Unlike traditional media repositories, Wikimedia Commons is free. Everyone is allowed to copy, use and modify any files here freely as long as they follow the terms specified by the author; this often means crediting the source and author(s) appropriately and releasing copies/improvements under the same freedom to others."
Below is "Sandra with Beard," 2000, Photography by Sandra Mann.
There are a lot of great resources on the web, from museum sites to Wikimedia Commons, where you can find collections of images. Hover your mouse over the links to find out what they contain. Have fun exploring!