I'd like to see more random dungeon layouts in general. While no map is ever exactly the same, they all have similar things in common, usually filling as much space as possible. Would be nice if you might occasionally come across smaller levels; perhaps even just two rooms with a down and an up, to make descending coc or ID a little quicker. Also randomised architectural patterns instead of just boring squares. Also maybe vaults with more tactical positioning and traps instead of just rows of enemies.