Magnetic whiteboards. Good idea.
The room we are looking at is 4.6m x 4.2m. Both the 4.2m walls are clean (no windows or doors). On the 4.6m walls, one has the door which is right in the corner and is 1m wide (incl frame). The other wall has a 2.8m window which is right in the middle and goes pretty much from the floor to the ceiling.