Photographs, charts, and graphs can enhance your paper or presentation.
Typically, images from books, articles, and databases can be used, as long as the citation is included. Here is an example from the National Library of Medicine - Images from the History of Medicine database:
A few notes on using images: You may have heard confusing information about copyright. A common misconception is that educational use is always an acceptable exception to copyright law, but that is not true. If you ever have a doubt about whether you should use an image, err on the side of caution and ask permission! Many schools or school districts will have a policy on copyright, or person to contact to ask questions. With school districts publishing more information online and having a web-based classroom presence, following copyright law is more important than ever.
For a good discussion about education and copyright, see the five-part series, The Educator's Guide to Copyright and Fair Use, published by Education World.