From Destinypedia, the Destiny wiki
Ornaments are used to alter the appearances of certain weapons and armor sets. Weapon and Armor Ornaments are activated differently. Weapon Ornaments are sold by Xûr, Agent of the Nine for 25 Silver Dust each, and require 1 additional Silver Dust to activate. Armor Ornaments are built into pieces of certain armor sets, and require 1 set-specific token and 5 Silver Dust to activate.
Armor Ornament Tokens
List of appearances