I just discovered that if you're wearing the Arch-Mage's Robes and put on a Dragon Priest mask (I only tested it with Nahkriin) that you become invisible... but just you. Basically, the mask won't show up, but it still replaces your face render. Thanks to the Arch-Mage's Robes, you still have a hood, but you have to head or body, and can actually see down into (and even through) your clothes.

Its not game breaking or anything of the sort, but I still thought it worth mentioning.