Reflected in this mirror here is another towel niche. This one had to be framed out because it is wider than the space between the studs. But it gives room to store four full sets of towels and washcloths. If you look closely, you'll see that the bathroom door opens onto that wall. There would have been no room to even hang a towel bar without it interfering with fully opening the door.
Tip: Using white towels in this all-white bathroom provides a minimalist, soothing look. You don't have to go completely monochromatic, but a minimalist color scheme will help to keep a small bathroom from looking busy.