I have gotten no cosmetics as drops yet. Got that Ashava horn from the second beta though!
Semi off-topic: I’m still a bit confused about the loot goblin. I have still seen less than 10 of them after a slow (doing many side quests etc) playthrough of the campaign. And of the ones I have killed or almost killed, I think the loot is really lackluster for being such a rare and special encounter. I have gotten only 1-3 rares per goblin. And compared to what the legendary drop rate is throughout the game, the loot goblins seem to fill no function apart for being rare themselves.