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 pull down table. Super space saver, looks like a picture on the wall. This would be great in a small kitchen for two people, or a playroom for kids (make the picture appropriate for whatever room you’re in!) SO SMART.