I know that it's probably way too late to change this in the current game, but if you ever do a sequel it would be cool if the level themes were in a different random order on every play through. ie. The fire level, for example, wouldn't always be the ninth level, it could be any level; the game could even start with a fire level (or an ice level or a space level or whatever).
This would be easier to implement if monster strength and loot value was all procedurally generated based upon dungeon level, but alas, it is not.
Alas, This was my assessment as well (which I why I stated that its primarily a suggestion for any potential sequels).