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.
DIY Vintage Milk Crate Turned into Unique Ottoman Tutorial -- could use the plain wooden crates found at a craft store, plus thick or heavyweight fabric, foam, plywood. Could also add hinges to make the top open for storage inside!