I-OpenOpen Access Biomedical Image Search Engine
All images require attribution, and are licenced under various levels of Creative Commons licensing unless licensing is not listed on an image which means you should contact the journal. Collection is from The Open Access Subset of PubMed Central (PMC), a free full-text archive of biomedical and life sciences journal literature at the U.S. National Library of Medicine, the Indiana University hospital network, the Orthopaedic Surgical Anatomy Teaching, and the Collection at the USC Digital Library.