<http://schema.org/thumbnailUrl>
<https://drscdn.500px.org/photo/21604553/w%3D160_h%3D160_s%3D1/1472ef48b5419d4c68b1a5acf3445a3f>
<https://marketplace.500px.com/photos/21604553/matterhorn-by-philipp-hoerler>