Some ways to decorate living room walls include: hanging art, using wallpapers, displaying family photos, hanging tapestries, or installing floating shelves.

Some common ways to fill empty walls in a living room include hanging artwork, adding shelving or bookcases, mounting a television, or installing wall panels or wallpaper.

Popular wall decorations include paintings, posters, photo frames, wall art, wall murals, tapestries, wall decals, and shelves.

To make your wall space look more expensive, you can invest in quality frames or artwork, or use high-end wallpapers. You could also consider adding molding or trim to your walls, or using elegant lighting fixtures to highlight your decor. Using neutral or earthy color palettes and incorporating natural textures, such as wood or stone, can also give your space a more upscale look.

When choosing wall art, consider factors such as the size and color scheme of the room, the style of decor, and the personal taste of the individual who will be using the space. It's also important to choose wall art that complements the existing decor.

It depends on the style and personal preference of the individual. Some choose to decorate all four walls, while others opt to decorate only one or two walls. It is ultimately up to the individual to decide how many walls they would like to decorate.