We need to see all the items that are already chosen and pictures of the space posted here in jpeg format so we can enlarge aget some idea of the items you mention. Post in a comment DO NOT start another post .

This is the kitchen. The sinks are stainless steel and electrical appliances black and steel design, not yet delivered. Thank you!

I’d get the appliances and live with the kitchen for a few weeks/months. Pick a color and buy a few accessories. Maybe a rug. Do a lot of looking online and locally.

I was in a tile store yesterday and there are some really beautiful tiles using metallics.

That does look good!

I like the photo with the light aquamarine small tile backsplash. What about the bare wall above the isle table next to the window? Could I do that in the same colour, or would it be too much?

Cool kitchen! You can upload your picture to a site like Tilebar and use their visualizer. I posted some examples below. Once you see something you like you'll want to get samples and view them in your space.

I think on your sink wall, you could go straight across under the window and keep it to that height to the end of the counter, or tile up to the ceiling like last pic. I'd play around with a visualizer to see what you think.

Robin Egg Blue:

Jade:

Triangle:(I like this one but not sure with the floor)

And some metallics:

Blue Metallic

Black Metallic:(hard to tell in the photo but this one is kind of cool; of all these might work best with the floor and your dark window trim)