Size and Scale of the Panel Mouldings The size of the mouldings you decide on will dictate whether the room will light up or look stifled. The size of the mouldings directly depends on the size of the rooms and the number of elements contained in the rooms. If the rooms are large, then purchasing smaller mouldings would not be advisable as they will blend in too much and disappear. Large rooms look perfect when they are dressed up in deep and heavy panel mouldings which are proportional to the size of the walls.