White subway tile will be the most classic. That way you can do a lot of different things - let me suggest that you not install the backsplash piece as a backsplash, but use an angle iron on the wall screwed into the studs covered with subway tile and install this instead as a ledge about 10" above the deck of the counter. Check to make sure it won't interfere with your faucets there / allow access for cleaning below easily / won't interfere with medicine cabinets or mirrors - 10" up is just about right. That also allows you to have outlets below the 10" level that are rather hidden in the tile / run horizontally.

The shallow ledge is very useful for many elements in a bathroom during getting ready, and looks better to have tile next to the marble top instead of a standard backsplash - more like a piece of furniture - which is hte style you have chosen.

Great vanity! Carrera-look porcelain is available at Lowes and it's not expensive :)

Here it is :)