Dear Client,
We wish you the bests in your new flat.
One thing to mention is that you can close the space under the staircase completely with veneered MDF board, or use the built a door next to proposed empty (shelf) areas. or close it half way so it wont look so deep as in the picture.
since the staircase is the focus point of the flat and since it is a relative small space. I suggest to use glass handrail to give a modern look as well as it will not imply that it wants to occupy the space.