Are you planning on having anything else above the splash back - cupboards or open shelving? It would be nice to introduce some timber to add interest & warm up the neutrals. Glass for the splashback is a safe option (easy to clean, no grout lines etc) but it's been around forever - why not go for something a bit more modern, as you really have a blank canvas to work with. Inspo pics attached (image 2 has a slate like floor).

Have you thought of mirrored glass. We rented a $2 million dollar penthouse and it had a dark grey smoked mirrored glass splash back on both sides of a galley kitchen. It was amazing. So easy to clean as no grout and optically it doubles the size of the room. I could also watch the TV and what the kids were getting up to in the reflection of the mirrors. It works both with modern and traditional applications and cost about the same as a coloured glass splash back.
You could just go to a standard hight of an overhead cupboard then put some simple shelving (IKEA) up above it to display a few items on this would save you money on the glass and add some visual interest at eye level.
I would also do a black chalk board wall behind the door near the fridge. You can get magnetic paint (Masters) If you do two coats of this first and then the black board paint (found Dulux to be the best) over the top it becomes a magnetic blackboard. I see you have a high chair and your kids would love it.
Happy renovating.

I'm looking at your photo and I'm liking the grey colour in the tile right in the middle of the floor.
I'm a big fan of the metallic glass splash backs. Maybe choose two shades lighter.
Think the warmth and texture of the slate will compliment the modern clean lines you have chosen.

I'm a fan of the mirror as well. It's cheap and effective and super easy to keep clean. Otherwise you could save yourself the heartache of too many choices and use the same stone as the bench top which would keep simple and clean lines. Good luck!

You may want to have a look at Laminex Metalline. We used it in our kitchen in a light grey metallic colour and it looks great. It's easy to clean and cheaper than a glass splashback.

Mirror also for mine. From the pic, the area looks modern and maybe a little tight, so this would open it up.

The mirrors come in a tinted bronze, and a tinted silver. I would probably go with the silver, to match the fridge & sink. You may want to put some shallow shelves above their if storage is an issue, and an LED strip the length of the bottom shelf.