[Admiral_Young]

Looks kind of Thanos-y with the crown thing around it's head...we've seen the Infinity Gauntlet in "Thor" and Marvel showed it off at it's MCU display last summer at SDCC, so maybe they're connected to that. There have been rumours since "Thor" that Thanos would appear and have some kind of connection to the Frost Giants. Other than that I have no idea who they could be other than what I suggested above.