Couple of ESB things, rewatching. Does IG88 have knees? Is he ever shown walking in other media?
Secondly why does that one Snowtrooper behind General Veers have a solid helmet with like nostrils but the others have a fabric mask?
http://www.starwarshelmets.com/Original-Imperial-Helmets.htm
The General Veers scene may have been shot at a different time than the scenes of troopers invading Echo Base.