Paint the stairway walls a bold color, such as red or navy blue, to emphasize their architectural appeal. This trick is both easy and cheap. It also covers the entire expanse of the stairway walls. Use a color that you like and that ties in with the rest of your space for a cohesive look. You don't have to add any artwork on the walls. Just let the bold color shine.
Apply wallpaper to cover the tall stairway walls. Like the paint option, this allows you to fill the visual space without creating any clutter. Wallpaper also lets you introduce a pattern into the space. However, wallpaper usually costs more than paint and you also can't change it as easily.
Cover the tall stairway walls with mirrored tiles. They open up the space and make it seem bigger. They also reflect light so you get a brighter space. However, dust and dirt show easily on mirrored surfaces and the tall walls might be difficult to clean.
Hang pictures of the family and artwork on the tall stairway walls. You can follow the angle of the stairway incline or group the pictures in random arrangements. To avoid a cluttered look, choose frames of the same color or pictures of the same subject matter. Before actually hanging the frames, lay them on the floor to find an arrangement you like so you don't end up with unwanted nail holes in the walls.
Paste wall decals on the tall stairway walls. You can use large decals for maximum drama or intersperse smaller decals with picture frames and artwork.
Place small lights on every stair step to create some drama and make the stairway a focal point. These lights also function to illuminate the stairs at night.