WoW was spotted doing that in 2012. It contained information like the server IP, the account ID, and a timestamp. As far as I know, Blizzard has never commented on it, but one theory is that it's for troubleshooting purposes when a player reports a problem and includes a screenshot.
Xbox 360 home screen had a design of rings which served more than just design asthetics. They were for fingerprinting the Xbox incase of defects or even leaked screenshots
