Add a splash of colour or texture to a single wall is a great way to change the feel of any space, including a stairwell. Check out this project which took the back wall on a stairway landing and gave it a new, dramatic look.
This is a great look that you could alter with a lighter or darker stain, or even a paint colour. Imagine it in a dark colour with some contrasting prints photographs popping out on it. Get the instructions here.