Please see the following sources for royalty free and creative commons licensed
Medical Image from Unsplash
An aggregated search tool from Stanford’s Lane Medical Library that will find images from multiple sites and display them according to their usage restrictions.
Science Stock Image Library
Browse through thumbnail images of viruses, cells, DNA, anatomy, molecules, astronomy, and more. Each thumbnail links to a page featuring a larger version of the image and a detailed description. Select the “Buy License” link in order to purchase the rights to that image according to your intended usage (e.g. Academic).
Databases for UNTHSC Faculty that include Images and Media: UNTHSC Library