Open-i is an open access biomedical image search engine that searches images from PubMed Central articles as well as several special image collections. It allows for substantial search customization via filters.
NLM’s Digital Collections allow searching and browsing numerous document collections: Images from the History of Medicine, World War 1, Medicine in the Americas 1610-1920, and many more. You can also search the collections for only images.
The Visible Human Project created publicly available three-dimensional representations of a male and a female human body. These images include cross-sectional cryosections, CT, and MRI images.
The National Cancer Institute offers a collection of featured medical images in several collections: science & technology, childhood cancer, Spanish-language images and diagrams, anatomy, historical images, and B-roll videos. The full collection is also searchable.
The Public Health Image Library offers a number of topical image collections on topics like influenza, bioterrorism, lab science, and more. Also of interest are image subsets selected for their interest to particular audiences: health care providers, teachers & trainers, librarians & researchers, students, consumers, and more.