Since we already have decals for every item, let us make books or some other records that allow gathering decals into one neat album.
Now, I ain't gonna ask for bestiary or discovered item index unique mechanics (however amazing that would be to have it actually in haven) addition, just some sorting and searching ability for gathered decals (not gonna ask for e.g. stats or personal notes via parchment, but would be awesome too).
I always thought that although making collections in cupboards, displays, on walls or mannequins is nice, some kind of categorization (be it player or client made) and completionist-enhanced experience would be quite welcome.