Format
Artist’s name (first then last), the title of the artwork (italicize titles of paintings and sculptures but set all other titles in quotation marks), creation date, repository name (including city and state), title of the online site, format type, URL, access date (in parentheses).
Example
Rothko, Mark. Orange and Red on Red. 1957, The Phillips Collection, Washington DC. Artstor, JPEG, http://www.artstor.org, (accessed May 20, 2008).