The only ones I've seen at the Tower are Future War Cult, Dead Orbit, and New Monarchy. I think the other factions are in sections of The Tower that are not yet available. As of right now, the Factions are just glorified vendors. They just stand there and let you buy armor and weapons off of them. The gear and weapons look cool as they are branded with the Faction symbol on it, but Factions don't provide much of a purpose right now. I'm sure that will be expanded in the full game.