I would either do white subway tile or do a rustic brick. Both would make a beautiful statement in your space. And I would tile all the way up around the kitchen sink window.

Have you considered sheet mirror? Or back painted glass instead of tile? Both options are extremely easy care.

To simplify installation I'd be inclined to keep the backsplash material under, and on the sides of window to the bottom of the cabinets.

I agree with Wendy I think a subway tile would look beautiful with the farm house sink. I also like the s/s pulls you have chosen. I also like the look of tiling around a window. This is what I had in mind but with a light subway tile that would match your granite.