I went down to London last Friday for a “study tour” of the Wellcome Trust. (More on that in another post.) Among many other things I learned that the Trust are curating a rather lovely database of medical and historical images:
There is a wide selection of images, from photographs of cellular structures to adverts for cough medicine from the early 20th century. Most of the images are available under a Creative Commons BY-NC license, which means that you can use them for any non-commercial purpose as long as you credit the creator. They could be useful for illustrating blog posts, reports, or presentations, for example.