This is basically the medicine cabinet's version of a kangaroo pouch: It keeps small, pointy items safe when the door swings open and adds bonus storage to the tight quarters. Get the tutorial at Peapod Journal
When we renovated my daughters' bathroom, we tore out & replaced everything, except for the oak medicine cabinet. I removed the door & painted it the trim color and now the girls have built in shelves to hold extra hand towels and wash clothes.
Tiny bathroom remodel. Paint is Rock Gray by Benjamin Moore. Tile is Hampton Hermosa set on the diagonal. Sconces, medicine cabinet, sink fixtures, and train rack all Pottery Barn. Sink and toilet are Kohler.