Furniture in a room needs to be in proportion with other furniture as the groupings in the room need to be in proportion with one another. Keep in mind always the size of the room when deciding on proportions. You do not want a really large item in the room such as a grand piano that will dwarf the other items in the room. If you perhaps have a very large room then you might add massive furniture, and have marked contrasts in the room. Color is most important in decorating as you set the tone of your room with the colors you choose.
Color provides background and can create harmony and also accent and variety.
If you have a formal room you will want to use colors that will be subdued and pleasant. You do not want colors in each room to clash with one another. Colors can be used to change the size of the room through the eye of the person seeing the room. You can also do a lot of concealing with colors in the room. A room will appear to be restful if the colors are cool and soothing and have a quiet appearance.