The Loom will allow for creating various accessories and such, and there will be an alternate section for mixing armor/clothes with these accessories. Certain accessories have a listed section or more that they fill, but you can only have one thing in that area. An example: I add the Traveler's Bags to the Lower Body area, but I cannot wear the Champion's Belt unless I remove the Traveler's Bags. The way accessories behave is not becoming a new set of sprites, but rather being on an alternate layer of sorts that attaches to the armor. I don't even know if that's possible, but it would probably mean not having to make TONS of extra sprites. Various armors and helmets will have restricted area flags. Think of how if your helmet already has some kind of mask, you cannot add a Front Head accessory to that helmet. I don't know what I'm trying to say anymore.
Um... That thing about not becoming a new set of sprites doesn't make sense. Everything in starbound is a sprite. The rest of the suggestion was pretty cool though, it sounds like something that lots of people would enjoy.