A small and simple built-in shelf, from Better Homes and Gardens. You could even fit a shelf like this in between the studs in the wall, making it a pretty easy DIY project. It could work in my powder room.
Revamp Bathroom Mirror: Before & After -- And it doesn't involve cutting or removing the mirror! Not that I have a mirror in the house larger than a Or a bathroom that large. My bathroom is about as large as that mirror I think.
Removing the Shower Door: Breaking Ground in the Master Bathroom -