How about glass? I like the wall color, so thought maybe glass?

Or a simple glass subway would give a bit of sparkle.

I like your island, pretty piece. If you like a crisp clean look then I too would second glass tiles. Go with a color to contrast all the white. A light gray to pull the vein coloring from the island..

My first suggestion was a glass sheet, just to clarify. My second was glass tiles.

Like mesh mounted glass? Something with movement and pzazz? That could be fun too!

Gorgeous kitchen! I think glass is too modern. Take a look at Winchester Tiles, an English tile company with US distributors.

HERE is their houzz page

Hands down, white subway. You have so many other statement pieces happening, let those be the standouts.

You might consider doing a plaque behind your range and pull from your island countertop. A herringbone pattern can add some interest an texture.