Toilet room such a dark paint, I wouldn't. White items will show more, against so much contrast.

I love the dark navy, but it can be overpowering. In your inspiration picture, only half the wall is painted that way because of the wainscotting. Perhaps you can add wainscotting in your bathroom, or add a chair rail and paint half the wall white and half navy.

I'm also considering tiling the back wall with mosaic. Not sure if the mirror is too large though. Maybe I can turn the mirror vertical (or possibly switch to a round one) and install two sconces on either sides. Does anyone have a similar style bathroom with an arch like that? Would love to see some finished products if you have any.