I just added one-time use items, actually! You can buy a health potion that you use from your inventory, but I am looking to add a lot more. Adding an item-chest is a good idea!! Perhaps each level of the dungeon could upgrade the chest too so you can get more out of it. I lament that the shop occurs after you win a dungeon because you might not even get to play with the extra items. Adding a chest to discover could whet the appetite for it!
Different shaped dungeon layouts is also on my todo list -- I want to also add biomes so that maybe the monster variety could change with the map/biome. I can see a monster that only lives in dead-ends, or only appears in certain biomes.