Light from above and the side washes across a surface to change how we see and understand that surface. Every variation in texture, joint line and piece of the surface is highlighted dramatically. We get a sense of how the wall was built and gives structure to the spaces.
Natural light washing across the surface from top to bottom makes this stairway a place to be, not just a place to walk through. In fact, placing a window or skylight at the top of the stairs is one of the most enriching ways to bring natural light inside. Think about what's more enjoyable — a stair that is bathed in light or one that's closed in by walls.
With the source of the natural light from the sides and above, the play of light and shadow across the wall is all the art work needed here.
The source of the light doesn't have to be visible. In fact, there are times when seeing the skylight is akin to the magician revealing the secret. It only takes away from the magic.
A brick wall is a natural to be washed in light. The texture and overall feel that these bricks were stacked by hand comes out when lit this way.
Certainly washing a tiled wall in light is an effective way to add beauty to a bathroom. Providing a slot of light that allows the tile to run up past the ceiling line gives an incomparable sense of spaciousness.