I wouldn't accent that wall behind the toilet, as that's not a space I'd want to call attention to. I would look for ways to incorporate more of the pretty vanity color into the room instead: Towels, a new shower curtain with that color in the mix, and perhaps in artwork.

I agree on no accent color. Put a decorative air freshener in the outlet by the toilet maybe.

I think you should paint the base around the vanity the same color as the vanity. You can still leave the rest of the base white.

@kate That’s a great idea! I suspect the seller did that to raise the cabinetry.