I would stay with one marble only in a bathroom. Pick one. Wouldn't put the greenish floor marble in that picture as a backsplash to the carrara vanity. If you mean the bluegreen wall tile as backsplash then yes use that with your carrara vanity.

Using the white subway with carrara and adding color as paint would allow color changes down the road when you tire of a color.

Well ... I dunno. White subway tile is a true classic, but this other ... this other is absolutely stunning, IMO. I can see why you've fallen in love with it. The only downside I can possibly see to using it in your shower is that you're then locked into a certain color scheme, which wouldn't be the case with the white subway tile (I personally wouldn't consider that a downside because this is one of my favorite colors and can't imagine tiring of it, ever). Sure, you could paint the walls in a "spa" shade, but that's not going to create quite the same impact as that tile would.

I'd try to find a way to make it work, although I understand that your DH needs to be on board too.