Great idea for a thread, Booman!
Those guys are officially called spacetroopers and have had action figures in recent years. I’ve seen behind the scenes photos of them being filmed, (back in the states just like the Cantina inserts) and the backpacks and airhoses were pretty much cobbled together as they were never going to be seen in closeup. (My Google Fu is failing me tonight, but the pics are out there.) The hoses just tuck in under the helmet. One of them was played by Joe Johnston.
Damn, I guess I still have a lot to learn. At least I managed to find that BTS shot you mentioned though! I did some more digging and found out that one of the cylindrical parts on the backpack also appears on the Death Star surface, which totally proves the “cobbled together” idea. I guess the person tasked with making the backpacks just saw that part sitting in the shop and said “eh, that looks good enough”.
Also while we’re on the topic of Mon Calamari…
This clueless background guy doesn’t get nearly enough recognition!