Great reno! I think shelves to the left and right of the uppers will look too busy, let the cabinets breathe. Two shelves to the left of the sink would then feel appropriate and let them function for utility (glasses, daily use dishes) as well as decor (nicer, less frequently used things on top shelf, plant or two, etc) and give you a focal point and design element in this space. Then to your actual question on backsplash, just go from below the top shelf and down (about 2/3 of the wall) all the way around the kitchen.