Nobody can really make a suggestion without photos of all the finishes -- ideally, photos of all the samples in the same photo, so the lighting is the same. Floors too. But generally, if there is pattern in your counters, you try to highlight that with a color in the backsplash that brings out a tone in the stone. However, if your counters are fairly plain, you could pick just about anything -- white or cream tile, colored glass, gray...