The following link takes you to a site with great examples of how to cite images using Chicago Manual of style in your papers. You can also consult the Chicago Manual in sections 12.31 - 12.51 for directions on how to write captions and credit lines.
Images can enhance almost any presentation. Some of the online encyclopedias and articles will have images, but it is not always possible to copy or save them because they are protected. Here are some other ways to find images.