On a random level Treasure Vaults are supposed to be 'good' and Graveyards 'bad'. However, I would personally prefer a Graveyard to a Treasure Vault, as Graveyards are pretty easy with a competent party, whereas Treasure Vaults don't pay out too well.
I know there is one level those which many knights strive to avoid, and those are the Candlestick Keeps. They are pretty hard and have a relatively low payout.
My suggestion is to make Graveyards a normal level, and put Candlestick Keeps in random levels as the booby prize.
I could get behind this.