Google Images Quietly Adds Face Filter
For example, a search on paris returns results of Paris, France, the Eiffel Tower, Paris Hilton and others. A search on paris but with “&imgtype=face” appended to the end, returns results mostly of Paris Hilton and other faces, because they match face results.
Another example is a search on google that returns mostly screen captures of the Google home page. If you add the face restriction parameter to the URL, you get pictures of people and faces related to Google.