Hi there Jack.
There is an announcement at the top of the forum about what to do to assure getting as many responses as possible.
The announcement leads
to this post (click here). Actually, several people, who are experts on this forum, will most likely not reply if you don't do what is written in that post. Many others who are very helpful, will most likely not reply out of respect for the moderators' wishes.
Seriously nobody here knows?
That's right. Nobody here knows, since none of us designed and built those studios. Fabric is frequently used to hide the actual acoustic treatment, which can go back a very long way behind it: some treatment is several feet deep. So it is impossible to say what might be hidden behind that fabric: it could be a set of acoustic hangers 5 feet deep, or it could be superchunks, or it could be Schroder diffusers, or poly-cylindrical diffusers, or Helmholtz resonators, or membrane traps, or simple absorption. Or it could even be just plain old drywall, covered with fabric to look nice. The only way you can find out for sure is to ask the people that built those studios.
Even then, even if you did find out what type of treatment is hiding back there, there is no reason to believe that the same treatment would be suitable for YOUR room. Every room is different, and the treatment has to be correctly designed for each specific room. Just because something looks nice or works well in someone else's room does not mean that it would be any good at all in your room. In fact, it might even make things worse. Put the wrong treatment in the wrong place in a room, and you can indeed make a bad room worse: or a good one, bad. For example, you often see QRD diffusers on the rear walls of large professional studios, so some uninformed home studio builders try to put the exact same diffusers on the rear walls of their tiny garage conversions, then wonder why it sounds like garbage!

Or they don't see any bass traps in the corners of some professional studio they like, so they figure their room can do without bass traps too, then they can't figure out why their mixes sound so thin and lifeless, when played on other systems, outside their studios.
Treatment is designed specifically for each individual room. Nine times out of ten, copying something seen in a different room simply will not work in your room. Either it does nothing at all (which means you wasted a lot of money and time), or it damages the room acoustics, leaving it sounding more unbalanced than before.
I'm very much a a beginner in studio design, so any help would be greatly appreciated!
I'd suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais. And also read John Sayers own work, right here on the forum
http://johnlsayers.com/Recmanual/index.htm
All of those are great introductions to the science of acoustics, and the art of studio design.
So my basic suggestion would be to not worry too much about how other people have treated their studios, but rather to concentrate on how you need to treat yours.
- Stuart -