<http://schema.org/image>
<http://rack.1.mshcdn.com/media/ZgkyMDEzLzEyLzA0L2VkL0dyb3Vwb2ZQaG90LmMwMzZiLmpwZwpwCXRodW1iCTEyMDB4NjI3IwplCWpwZw/3fd621af/370/GroupofPhotos.jpg>
<http://mashable.com/2013/12/03/photo-tagging-algorithm/>