This is something that's in a game called Sanctum. Basically at the end there's a screen that shows stats for all players. For here you could make the screen appear when you reach moorcraft/emberlight/the core in case people are afraid of people getting kicked from teams. Perhaps instead of having a screen come up automatically there's a NPC on those levels that you can talk to that will bring up the stats. It could have stuff like total damage dealt, total life lost, number of enemies killed, number of times died, number of times revived an ally, number of levels completed, number of attacks blocked. Stuff like that.

The important thing is to not have it affect anything. Like no crown bonuses. It would be just for fun.