How about appending the display name of the person who uploaded it? That'd be a nice feature if you need to remove pics by a troublesome user or something.
PersonsDisplayName-OptionalSiteName-#-pic.jpg
e.g., jgeoff-ubbdev-1-nudepic.jpg
Though I would think you'd have to remove spaces from the person's display name. And/or use their login name. And/or shorten their name to say 6-8 characters or so...
