Alright people may have already found this easter egg but I just found it and I thought it was kinda cool so here it goes:

When you are playing Operation Metro on the Multi-player, there is a random photo booth that is accessible from the ticket hall.

If you decide to enter this random photo booth, you can press the "Enter Vehicle" button and the booth will flash and it will take a picture of your character. You can do this until you get bored and or killed.