I did a lot of searching to attempt to find the source of that image for you but unfortunately I could not. That being said, I have found it on dozens and dozens of websites as early as 2009. I could not tell you the copyright for it, but the widespread usage on a number of legitimate foreign sites (as legitimate as they can be without sourcing their materials) tells me it might very well be free to use. Best of luck on your thesis!
Via Archaeology Blog dedicated to the greatest ancient culture – Mesopotamia.