I'm only listing characters who are truly in that faction. Using my character Menora for example, she supports the Stormcloaks but is not an official member of their ranks. So unless someone is an official member of a faction they're not going to be shown on the list.

Also, reviewing the list, I don't think I can accept any more Thieves Guild members. We need more characters in other factions if more people sign up or if more characters are added. I know there are some factions I'd like at least of of my characters to join, but I have to work that out with people in those factions and/or play the NPCs needed myself since no one else has claimed to play them.