Most people don't think about proportions,scale and balance like designers do. The average person can tell you something looks incredible and they can also tell if something doesn't "feel" or look right, when this happens, chances are there is an element of scale and balance that was overlooked.
We designer's know that when you have a wall this big (see above: 18' wide wall x 10'tall) it is nearly impossible to find furniture (i.e. bookcases and desks) that fit the space without making them look out of scale. For times like these, it is best to go custom and fill the wall.
I love custom mill work and custom built-ins for that very reason, making things fit a space perfectly.
Above is a bookcase I designed to fill the entire wall. We spent several hours carefully designing the spacing , width, heights,thicknesses, etc... keeping all the proportions just right. Doesn't seem like it would be a big deal, but it is. This wall unit could easily look out of proportion if it wasn't for careful planning. The long desk (11'-6") that intersects with the bookcase, also was revised several times until it was perfect on paper .We also had to keep in mind how BIG we could actually make things so that they could fit through the hallways and doorways once built . ( I put myself in this picture above so you could see how big this wall unit is.) Once it was perfect on paper, it went into production where I had to make some additional adjustments at the wood shop before it was lacquered and delivered.
Although I filled the entire wall, it does not feel heavy and over powering in the space . Why? Answer is because the proportions are right. Sure, painting the bookcase & desk a white lacquer like the white walls helps with keeping things light and airy, however the proportions of the woodwork is what makes this space work.
Proportion is simply Scale and Balance , it is the relative size of areas and objects, and how they relate to one another. They are important factors to consider when designing any room ,especially for a wall this big . For Designer's this is second nature. Try these simple tips on your next project and see how much greater your space can be.
When something doesn't "feel" or look right ask yourself :
How can I balance the space / room?
If one object is big on one side, balance it by putting another large piece on opposite side.
Is everything the same height?,weighing the room down and making it feel heavy? If so, Varying object heights is another way to balance a space. Tall objects, low object, keeps your eye moving and keeps room from feeling "stale".
Is the scale of one object relating to the other? If not,sometimes simply re-arranging the objects balances the space.
Color is another way to balance a room. If you have a pop of color, be sure to "sprinkle" it around the room space, so that it is not only in one area. It also keeps your eyes moving.
If you have a focal point in the room,example a fireplace...Be sure you have one or more pieces about the same scale in the room that help anchor your focal point.
Good Proportion is what separates good design from great design.