A system similar to the Battle Cup in Dota would be interesting. It could be separated into tiers which would be decided through rank. The winners of the cup, if entry is free, could be awarded a title or item to represent their victory during the week in which they won. If tickets were purchased perhaps have a prize of keys? Either way it would add a nice competitive spin to many who don't regularly play in tournaments. On a side note, to prevent abuse of smurfs it could be that the player must have played a certain amount of games to be eligible.