If available, provide the photographer's name, the title of the work in italics, the date of composition, and the medium of the piece (so, "photograph"). Finally, provide the name of the institution where the photo can be viewed. If this is a website, cite the website as a container.
O'Halloran, Thomas J. [African American school children entering the Mary E. Branch School at S. Main Street and Griffin Boulevard, Farmville, Prince Edward County, Virginia]. 1963. The Library of Congress. Flickr, https://www.flickr.com/photos/library_of_congress/15356487161/in/album-72157647638322417/
Content adapted from Purdue OWL: https://owl.english.purdue.edu/owl/resource/747/08/
Remember, if you use a library resource like CREDO or EBSCO, the database will generate citations for you (even for images!). Here are some other resources to check out:
Purdue Online Writing Lab (OWL): My favorite citation resource is easy to use (just drill down the links on the left) and extremely thorough. This link goes straight to the MLA guide, but use the links of the left to navigate to different sections.
OWL on Youtube: Short videos teach you the basics of both major citation styles.
EasyBib.com is another good resource for APA and MLA style. Use the guide instead of the citation generator--it will save you time and effort in the long run.