This picture was posted from official account: https://www.facebook.com/profile.php?id=267761909937344 (third number) so it looks legit

Correct me if I'm wrong but that picture doesn't really say anything. Each one of those machines could still be running 16 VMs

is this from an actual hetzner datacenter?

yes.

it's linked on: http://www.facebook.com/HetznerOnline

and probably shows: http://www.datacenterpark.de/index_en.html

Here's a list of all data centers: http://wiki.hetzner.de/index.php/Rechenzentren_und_Anbindung...