I always liked the idea of a flash chess game but to survive Kongregate you'll need a serious twist and I have some suggestions:
Make it RPG!!!! Winning matches against gradually difficult NPCs would level you up, gaining money to travel to different competitions and to buy better looking pieces or any other chess gadgets, making your way to be the ultimate GrandMaster.
But first you need to learn how to do En Passant and proper castling.