Under the slots I proposed in #5, I would say a bindi could take up a Face feature-slot, but equipping one would add a second Face feature-slot (the bindi is just a sticker or paint, so there is plenty of room for other face features). But if it is jewelry suspended by a headband or crown, I would use the Top of Head jewelry-slot.
It shouldn’t be a problem since glasses/eye accessories have their own equipment slot. 
~Max