Handrail lighting detail -- LED lighting i like how this goes with the concept of how lines interact with a space.
Under stair storage - create a craft room right in that little space next to the stairs! All the storage you'll need will be right there, so the floor space if free for your work!
If put laundry under stairs, could use mirrors on door. contemporary living room by HP Rovinelli Architects
A living room is an another place at a house where the staircase could be. In order not to waste any space you can organize a home library under the stairs