Format if author is known:

Artist’s Last Name, First Initial(s). (Date). Title [Description]. Source, Location. URL

Example:

Shaunessy, M.R. (n.d.) Babi Yar [photograph]. Creative Commons. https://ccsearch.creativecommons.org/photos/104d40e9-c2e3-4274-bed7-d71103f64126

Format if author is unknown:

[Title][Description]. (Date). Source, Location. URL

Example:

[Maimonides teaches about the 'measure of men'][Manuscript illumination]. (1347). Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Measure_of_men.jpg