This was stewing in my head for a while, but I feel it should be brought up, at least: Adding custom graphics to T-shirt fronts. For example, if you were to make a mascot character for Mannequin, if she's wearing a T-shirt, you could add an AR14 or Mannequin logo to that.
It would definitely have to use PNG files, since they can render transparent pixels, as well as JPEGs. It could open up a wide range of "fictional" cosmetic quality, from amateur (an obvious rectangle from a JPEG) to professional-level (a seamless PNG graphic) designs.