Oh that sounds horrible, I like a little personal stuff. Honestly no one cares about my space and it is a freakin' disaster. I have a small room for me and my assistant and we store pretty much all our supplies for programs there as well.
I know my ex worked in a classified environment and they had to clear the desk every night. Many things had to go to a safe. However I think he was allowed to put his phone his own way and have a photo up.
I just read an article about stupid sh** that makes good people want to quit. One is to take a problem of one or a couple people and then turn the solution into a policy for everyone. Another was being excessively controlling. I don't know if your new guy is just controlling or if they can't manage that one messy desk person. It is poor management skills to make everyone follow a rule to manage one employee.
IL - I had a 'pens without caps' rule. It came after pen leaks over and over.