All the teams have a real-life counterpart behind them. The reason they've not been given away is to maintain the aura of the contest. Though I reckon when screen-shots start going up you'll probably start figuring it out yourself. As for now all we can reveal is that the teams have been assigned based on strength of the area and to an extent, their fan support. The more central characters will be given to priority for the best players on their respective teams.
Just as an example,
Were Angband to be Argentina. Melkor would be Crespo.
Think along those lines and it'll clear it up for you.
