There are two cells in the corners, it is assumed that monsters live there, you yourself can decide which and how many. It could be minotaurs or undead, but it could be anything that fits into one square.

Also, I did not add explicit traps to the map, you can place them anywhere you want. The circles on the floor are triggered traps. I also advise you to decide in advance about the traps in the chests, are they reusable?