That is a neat looking horse. I have gotten 3 different sets of tack. A merchant tack, lamplighter, and something else, but I cannot recall it off the top of my head. The lamp lighter is pretty cool though.
Made a necromancer just because I got that horse and it didn't really fit my druid. I'm hoping for the Butcher's trophy cleaver, but only encountered him three times so far and it dropped once but for another member of my party.
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.