I think it is pretty together!

They compliment each other and your kitchen will feel slightly more rustic than if you use white subway, which is a bit different.

Pretty! Agree that the more natural stone will give it a more rustic feel.

It is pretty! But I urge you to think about having to clean that rough stone. Grease, dust and grime are going to love that rough surface. If you love it, go for it! But be aware that it will be difficult to clean.

GREAT point, rachuba. I changed my mind on a backsplash selection in our new build last year for JUST that same reason on a little raised tower right behind the sink in our kitchen island. Was thinking of how spaghetti sauce dish water would be a pain to manage on the light colored natural stone. If it can be sealed, MAYBE, but I've also heard that sealant can give stone like that a permanent "wet" look. Just some things to consider.