Give the name of the artist, the title of the artwork (in italics), the year it was made, and where it lives (museum, gallery, etc.). It’s fine to add other information if you know it, such as the size and medium. If you found it online, give the date you found it and the URL. If you found it in a book, cite the book and page number. You can either put the information in a caption near the image or in an endnote or footnote - no need to do both. Images are not usually listed in a bibliography.
Figure 1. Cornelius W. Borah, Two Unidentified Civil War Veterans, ca. 1880, photograph, accessed May 17, 2019, https://www.loc.gov/pictures/item/2017660606/.
Figure 1. Name of Photographer, Title of Photograph, year or era it was made, medium, accessed date, URL where it can be found.
Figure 1. Cornelius W. Borah, Two Unidentified Civil War Veterans, ca. 1880, photograph, accessed May 17, 2019, https://www.loc.gov/pictures/item/2017660606/.