add wood wallpaper to the kick plates of the stairs. Those rolls are expensive but you would only need one. Not practical with white treads though, it will be stuffed up from black shoe soles in no time.
I always hated all the wasted space under stairs.especially like the open shelves & the bed (great for a guest "room" spot under stairs in a finished basement) & the.well guess I really like them all! Wish I had stairs!