Monochrome chic. Simple is best in a narrow hallway. White painted stairs make them appear wider and the grey runner is both practical and elegant. Seek out a slim console - vintage or modern - thats useful and decorative but not space-consuming.
Tone on Tone: I chose a wool sisal style staircase runner with very narrow binding. It's installed about 3 inches from the sides (and cut out around the newel post) in the Hollywood style, which is tailored and bespoke. The big area rug is the same, but with a different binding. Larger area rugs do wonders for small spaces!