<http://schema.org/thumbnailUrl>
<https://drscdn.500px.org/photo/19406671/w%3D160_h%3D160_s%3D1/d0caff72771ea6f5f0518ce27de4c08d>
<https://marketplace.500px.com/photos/19406671/monochrome-nature-by-tom-engelhardt>