From The Boy Kings, by Katherine Losse, pg 25:
For example, on Mark’s birthday, in May 2006, I received an email from his administrative assistant telling me that it would be my job that day, along with all the other women in the office, to wear a T- shirt with Mark’s picture on it. Wait, what? I thought, he’s not my god or my president; I just work here . The men in the office were told that they would be wearing Adidas sandals that day, also in homage to Mark. The gender coding was clear: women were to declare allegiance to Mark, and men were to become Mark, or to at least dress like him. I decided that this was more than I could stomach and stayed home to play sick that day. I was the only one. The other women in the office, including Mark’s girlfriend, who did not work at Facebook, but had come to the office to celebrate his birthday, happily posed for pictures wearing identical shirts printed with Mark’s picture, like teenage girls at an *NSYNC concert or more disturbingly, like so many polygamous wives in a cult.
Gawker apparently posted photos of this at the time but I’m struggling to find them.