Per artist's comments, that's Nei from Phantasy Star II, not Karen Erra from PSU. The bearded guy is Jim Raynor from Starcraft. I don't see where anyone's seeing Pac-Man, though.
I think that completes everything significant, but I'm leaving the tagme in place in case I missed something, like the claimed Pac-Man sighting. (Also, the Arkanoid tag should be a copyright, but I can't edit that.)
I don't know if I should feel proud or feel old for being able to identify the kilrathi in the background. Thats Crown Prince Thrakhath nar Kiranka from Wing Commander II-III. I won't tag it though, thats a wee bit too obscure IMO.