The name, caption, or your own description of the image acts as the title.
The official title of the artwork is italicised, but a descriptive title of an image is unitalicised and in 'single quotation marks'. Use “n.d.” where the date of the image is unknown:
Format:
Artist, AA year created, Title or 'Description', Medium (Photo etc), Name of site sponsor site, place of sponsor site if available, viewed date Month, year, <URL>
Example:
Cher, V 2005, Sad teenager, Painting, Museum of Bad Art, Needham, MA, viewed 30 October 2012, <http://www.museumofbadart.org/coll6/image03.php>
Rothgeb, E n.d., Ronan the pug, Painting, Museum of Bad Art, Needham, MA, viewed 30 October 2012, <http://www.museumofbadart.org/coll8/image04.php>
In-text citation:
But are artworks like Sad Teenager (Cher 2005) and Ronan the Pug (Rothgeb n.d.) truly bad, or is it a matter of opinion?