Fan sign
A fan sign is a device used to make sad, fat, 
unpopular LiveJournal users feel popular and cool online.
Fan signs are created by friends of the LJ user, usually a 16 year old girl with big tits holding a sign that says "$LJUSER IS SEXY" covering their rack.
Fan signs are also used by goth alt models who claim their pictures are posted elsewhere by people dying to be them, or simply to attract unwelcome solicitors for the "real" owners of the images.
LJ user unpopular was one of many to request this of her "fans" and of the communities she moderated.
Other sites use fan signs, though with far less regularity. The hypocritical emo kids from Vampire Freaks love them some signs, so long as they're written in blood.