There is one potential item of loot, but it exists as an easter egg with an extremely low probability of proccing and it just gets you 225 electrum when you sell it. For all practical purposes, the rewards of the quest are the things you receive when you complete it. The only reward you get for completing the maze before the game does it for you is the satisfaction of it.
PS. When I say extremely low, I mean it's a one in ten thousand chance of encountering it any time you enter one of the rooms that isn't part of the 'correct' sequence.