The sofa is positioned on an angle against a corner wall, creating an empty triangle space behind it. The ceilings are high. I need to put something behind the couch so that it's not just dead/empty space. I have a sofa table behind it for now, but everything I put on the table seems too short against the high ceilings. I have thought about a tall plant. Can you think of anything else? Maybe something on the walls?
I had exactly the same problem in our living room which has 2 story high walls. I too use a sofa table behind it with a plant perched on some books for height, a tall statue and a lamp. I also found hanging art on one wall of the corner and a ledge with some tall items placed on it creates a vignette and brings the ceiling down.
A sofa table, a book shelf that is the length and height of the couch, a cedar chest.
You could do a couple of different things - add a ficus tree behind the couch and get an up-light . I have also seen people use those screens with the paper and do the same thing with the light. Another option would be to get some floating shelves to put on the 2 walls and lean a picture/print against the wall on the shelf, add a vase ...etc. If you need more height with the sofa table you can get some 2 inch wood blocks to raise it up a bit - or buy inexpensive decorative box's ( from Tuesday Morning, Kmart, Target ) and elevate anything you have on the table
The sofa table is fine and you could add tall vases or large pieces of artwork as well. But it is more important to add a large drama piece of artwork to the wall behind or a large series of related pieces. Take advantage of the ceiling height by drawing the eye to the drama piece on the wall. It will bring the room into focus and show off both the lower decor and give the eye great visuals as well.