What color are the cabinets - they look creamy/taupe-y? I probably would just go stainless - I feel like black will be too much contrast when in line with your cabinets (the counters look nice), and white wouldn’t go.

As for the backsplash, generally that 4” bit you already have on the wall is your backsplash. Unless you’re planning to remove it?

Stainless steel appliances.

Stainless

If you are looking for backsplash tiles, we offer stainless hexagon backsplash tiles that have both warm and cool tones. It might be worth a look! https://www.houzz.com/products/4x11-honeycomb-matted-metal-peel-and-stick-backsplash-tile-set-of-3-brushed-st-prvw-vr~100903589. Best of luck.

I wouldn't put another backsplash above your cabinets. You might want to consider a decorative-type one just over the range, kind of like a photo. A stainless one might be something to consider if you get stainless appliances.