Second, so many of these pictures are stills taken during a movie shoot, so when I have a signed contract with a photographer, I get the model's stage name (usually) which helps me with search engine traffic; and often, the name of the movie is listed as well, so then I can say, "Come and rent this movie at MANcheck Cinema with so-and-so, and here are some of his other movies."
Excellent point ... and any leverage you can find can't hurt!