I had storage under my stairs in our previous home and am having it done again. I loved it. I put seasonal things such as candles, wreaths etc., that I could not put in the attic in there. I had considered making shelves/built-ins in the hallway under the stairs but I decided I would rather just have storage. It is also a great place to store the vacuum cleaner. Mine is open all the way under the stairs, the framer was going to wall it off and make it like a coat closet but I felt like that was wasting space. IMO it's great.

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

I think a comfortable distance between the island and the counter is around 42". It seems that you have only 30" between your cook top and the counter. I might be a little too tight. The wall between the entrance and the kitchen could be 4' long instead of 6', you would then be able to move the island a foot which would give you more room between the cook top and the island. Could you switch the location of the toilet and vanity in your dad's bathroom so your enter facing a vanity instead of a toilet which is a lot nicer.

Seems weird not to incorporate it into the design -- I'm all about having things "look intentional" rather than working around them later. Like could the island have connected to this, rather than extending past it? or been L-shaped, so there's room for an extra stool, and also a wall cabinet? Anyway, hard to discuss that in the abstract without kitchen plans. I'm with miacometlady's original advice to not worry about it right now, and decide how to deal with it once the bulk of your kitchen is in place. You might find that you hardly notice it, with all the beautiful new finishes, or it might seem obvious to put some stainless or glass shelves there, or maybe simple is best and one simple hanging picture does the job. Don't stress about it until After. :)