Please disregard the second attached picture with the hanging pendant lights. I attached it by accident! Oops :O

I would maybe go with something like a neutral travertine or stacked stone. I could even see something with some reds/greens/browns.
http://kitchen-backsplash.com/backsplashes/3x6-multi-green-onyx-subway-brick-polished-tiles-for-backsplash-shower-walls-bathroom-floors/

I would use a honed travertine in a light walnut type color. Use a warm toned grout that matches the stone. Could use 4x4 tiles, but I prefer the 2x4 subway.

I think a glass subway tile would look nice in a cream color

I agree with Deborah Butler — something with light warm tones... And maybe installed on point (diagonal grout lines) to counterbalance all the right angles you already have going.
I'm thinking something like the Taupe 4x4's (carrot cake photo) but installed on point (like the background tiles in the ornate range hood photo).

I'd get some red in there... Maybe those small square mosaic tiles w various colors and a few red ones popping through

Long overdue but thanks for the advice. We went with travertine on a diagonal as suggested and it came out nice!