<http://schema.org/thumbnailUrl>
<https://drscdn.500px.org/photo/17421861/w%3D160_h%3D160_s%3D1/1fe4532c41dcd2dcbd8a51f55b43d5a5>
<https://marketplace.500px.com/photos/17421861/sunset-in-cologne-by-thorsten-jung>