Necessary, but basic. You could hang a picture on it or something.
Big wall with nothing in it
A bit better than the small one. It’s greater size making it ideal for sideboards, book shelves, and the like.
Everyone loves a floor, all carpety and warm, but there is no denying that the floor is already there when you start building.
The wall with a door in it
Doors are great. If you want to get into, or out of, a room then a door is the best way to do that.
The wall with a window in it
A window brings light into a room and lets you look out of it. You can, at a push, achieve the same effect by leaving a door open but you run the risk of letting the cold in. The advantage the window has over a door is that it is see through, which means you can see through it. In a nutshell, while you can’t really use a door as a window, you can use a window as a door, so windows are better.
No matter how much you like the other five sides of a room, there is no arguing with the fact that without a ceiling they are going to get rained on. It is the ceiling that brings everything together, truly turning what is just some walls into a proper actual ‘room’. So hooray for ceilings, and all that they do for us.