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.
ARTstor is the database by which you have access to thousands of images related to a variety of disciplines in addition to art, art history, and classics. This is also the place to gain access to our licensed images from Scholars' Resource as well as locally produced images for the Teaching Collection.
NOTE: "Users can create a registered user account when accessing ARTstor from a valid IP address (either on campus or through a proxy server - VPN). Each registered user account allows for a 120-day Remote Access Period during which it may be used to access ARTstor from any computer. Each time a user logs in to his or her account from an authenticated IP address, the 120-day period is reset."