Freely available collection of images, image collections, and multimedia files from the Centers for Disease Control and Prevention.

Open access database of medical images from the National Library of Medicine.

Open-i service of the National Library of Medicine enables search and retrieval of abstracts and images (including charts, graphs, clinical images, etc.) from the open source literature, and biomedical image collections.

After you enter the search fields of what you are looking for, scroll to the bottom of the screen. Last search filter will be usage rights where you can search for images that are: free to use or share, free to use or share even commercially, free to use or share or modify, and free to use or share or modify, even commercially.

Repository of open access images via Flickr

Provides media files in the public domain and operates under the same principles as Wikipedia in that anyone can edit or upload.

Search for photos by category.

Free icons and stock photos.