There's almost nothing you need to do in this room aside from going through it to get to the Garage or to the Guard Hall, as well as possibly picking up some treasure. There are also a few tarantulas in this room.
This room is very decorated, there are many paintings covering the walls and two large armors by the door. The room also has to pots containing coins and it is also filled with cob webs. Finally, there's an inaccesible door to the right of the room that Luigi may be able to enter in the final game.
Enemies in the Entrance