Consider painting the back of the shelves black first. Then stage the shelves.

Before dong anything radical like painting anything black, I would take black paper or black foam core and mount it there and live with it for a long while.

Something with some natural texture would look nice.

A beautiful wooden cutting board. A basket or glass bowl with fruit. A bushy plant.

On the top shelve, two large art pieces.

Please use things with curves, not all rectilinear.

If you are willing to do color but want a modern style, for the art work, think of a style like Victor Vasarely or Vassily Kandinsky or Yaacov Agam.

Start a collection of antique kitchen utensils?

Or a collection of anything really. I chose these funky teapots because it looks like the shelves in my dining room:

647-06377351em-collection-displays-recessed-glass-shelves-used-to-display-an-art · More Info

What do you like? What do you have? Use that. Done.

Architectural Digest is not waiting to shoot your kitchen. Put up what suits you. And change it 2 weeks from now if you want. They're shelves, not coffins; nothing is permanent on them. No big deal.

Is too late to install cabinets on that wall?

Your living room furniture is modern, so keep the kitchen simple and not over done. I would stick to the existing colors...white, gray and wood. I would add a piece of art on the top shelf to give it height...but not color. Cute baby!

How about a coffee or baking station?

https://decoholic.org/2014/11/06/40-ideas-create-best-coffee-station/

Your space is gorgeous. Since you don't need the extra storage, I would keep it very simple and place a few black-framed prints on those shelves. You can go black and white or use pop of color, vary the sizes, and overlap them to add interest. I'd also mix in a little greenery and wood elements, like a couple oversized cutting boards, to warm it up and tie in with your floors.

Beautiful kitchen. How about plants in ceramic planters? Among the plants that work well in the kitchen: Aloe-Vera, Chlorophytum Comosum & Aspidistra-Elatior.

Lovely kitchen! Put personal items on them. Picture frames of loved ones, seasonal decor, a coffee station / bar. Pretty dishes, artwork. A combo of all of the above. I love to see a little whimsy in a space to add a personal touch.

I would need the storeage but since you do not & I presume you don't like to clean & dust (I don't), I would remove the shelves and hang a large dramatic art work in the space.