A houzz contributor, not too long ago, had made a wine rack out of 4'x4' wooden pallets, that are used in the US to move a load of goods with a fork-lift truck. Perhaps they have them in your country. He cut them in half so they were only two feet deep and stacked them up to high counter height. The wood would be a nice contrast with your concrete, might add a little warmth to the space. cascio.offsite@gmail.com

Let us start begin with your preferred usage for the space. What is most desirable in your home (a space for storage, entertainment, work, etc.)? In my parent's home, for example, the area underneath their basement staircase is used only for storage. Although, it is possible to use spaces for multiple purposes. For example, a dining place that may compliment your kitchen (whether primarily for everyday seating or entertaining guests), may function as a dual space. If an lcd space is desirable, I would love to design some possibilities that will serve its purpose in completing your home. If you are unsure of what your function you want your space to have, perhaps it would be better to establish the mood of your space in completing your home. Is it a calm and tranquil space that you are looking to have or a busy and excitable space that you are looking to enjoy?

You really don't have the floor space for a stairway on that plan, even a spiral. If possible, try to squeeze out some space next to the entry door to avoid having it in the middle of the plan. It might not cost a lot of additional money to have the stairway as a bump-out along with the front door.

it appears you need storage. I would get with a storage professional on how to best utilize the space based on your needs.