There was a lot of inspiration in the narrow bathroom of the Hotel Allegro, where I stayed for one of my there nights in Chicago last week. From the wall to the tub there were 4 floor tiles - so I'm guessing 4 ft. The narrow marble counter with sink had plenty of room and the angled edge made for a more spacious feeling.
The mirror ran almost the full length above the sink.
Plenty of storage space below too.
Stacked subway tile didn't compete with the geometric wallpaper. Loved the pretty blue ceiling too.
A small profile light with simple lines and just enough space for a makeup mirror tucked in the corner.
One other note, the door to the bathroom was a split door that opened out, like small, solid french doors.