I wonder how we missed mentioning this really splendid resource: Digital Himalaya.
Click the link and go exploring. I spent an hour rummaging around, and came up with a number of treasures. Etienne Bock's "Coiffe de pandit," (Revue d'Etudes Tibetaines) is a case in point. Easily the most erudite study of lama hats in the open literature. You'll find your own treasures, so what are you waiting for? Everything should be like this.