Oh my gosh!! So I'm not crazy, that is what I saw in the lobby of matchmaking with my friends I told them and they didn't see it. And soon after deemed me crazy.
I saw that like 80 times and I thought it was a mask, I told my brother a couple days ago and he laughed. who knows though, it might not be.
No, this was put there on purpose, it's Bungie's little dorky cartoon Master Chief. You can even get a gamer pic, in color, of this guy.