Neriak Fourth Gate - Dark Elf Ornaments
The items you see on this page drop exclusively from the Dark Elf enemies found in Neriak Fourth Gate which is a zone that was added in the Call of the Forsaken expansion pack. These are Ornamentations which you can place in the Hero's Forge slots of your armor.
When you Inspect a piece of visible gear by right clicking it you'll see a Slot 5, type 21 which is separate from all of the other Augmentation slots on the piece of gear. This is the slot that Ornamentations go into. Unless you purchase the unlock from the Daybreak Store for your character this slot will appear as a green box that says "Buy Now".
As you might be able to imagine the Dark Elf Ornaments may always hold value depending on your server and who plays there. Someone on your server may really enjoy what the Dark Elf set looks like and thus want them for all of their characters. Alternatively you may find someone who just wants the achievement for equipping the whole set.
Depending on your server will really determine whether or not there is a market for these items. To give you an idea of what the market looks like on Firiona Vie I snapped this picture which shows you some of the Dark Elf Ornaments that are up in The Bazaar - the cheaper ones anyway.
Your servers prices (unless you're on FV) will be radically different than what you see in the screen shot above. Since on FV the Attuneable quality doesn't matter one bit - you can still drop the item anyway - it leads to our market being oversaturated on some things.