If you at any time take off your helmet or put it back on this will break your portrait. If you dye the item, cast a glamor over it, remove it or if it's a tome item and you've upgraded it these will break your portrait. I.E if you went and upgraded the Lunar Envoy's Justaucorps of Healing to Augmented Lunar Envoy's Justaucorpe of Healing even though the outward look of it hasn't changed the item tag in the game files has. Just pretend it is a more finicky version of the Fashion Report.