Ornaments allow you to change the appearance of Exotic weapons and as of Curse of Osiris,
certain Armour pieces.
Not exact matches
The big issue is that each
piece of
armour needs different resources to upgrade, which you'll have to farm from
certain enemies.
That's because in Breath of the Wild, you can not sell
certain armour or clothing
pieces.
Some
armour pieces and weapons come with decoration slots to further reinforce
certain passive skills and resistances.