IMO, I would base the system from a person's top 100 plays at these intervals, as these are obviously the hallmark of a person's peak skill
Say if the mean/median/mode of a person's top plays are (variant of the system the OP has):
0pp-50pp - Bronze
51pp-100pp - Silver
101pp-200pp - Gold
201pp-300pp - Platinum
301pp-400pp - Diamond
401pp-500pp - Uber
501pp-600pp - Elite
Again, you would use the same graphical features OP requests, and should have the option of toggling these for public viewing (shows on your profile or not).