"Something to eat? Drink? Of course these things are contrivances, like so much here, for the sake of appearances."
The Merovingian, The Matrix Reloaded
Batman has his Batcave. King Arthur has Camelot. The Enterprise has Ten Forward.
Every hero seems to have a home base, a safe location where they can relax and be themselves. Even the most frantic adventure story has moments in a quiet refuge so as to contrast the action before and after.
Firewall can certainly see the need of a hideaway for its sentinels. But the problem is that characters are essentially a kind of ephemeral, transient data. They can't even call their ever-changing forms home, let alone an actual place. Still, some of Firewall's psychologists can see the need for a home, even one that doesn't technically exist.
It was often useful for a Sentinel cell to meet up in a simulspace environment but this was usually a utiliitarian office, a basic default of the network. Firewall set about designing a more personalized environment.
The early versions of the 'lounge' were based on the nearest historical and mythical analogues to Firewall, the French Resistance and Scarlet Pimpernel scenarios were popular.
As were the headquarters secretly worked into existing games such as Alien Raider or Gilded Empire.
Eventually Firewall learned that each server and cell would personalize their virtual headquarters. This led to two minor advantages; the first was that only the regulars might know which virtual book in the virtual bookcase opened up the data crypt and impostors could be fished out ("So, you are part of the cell in a stolen morph, eh? Where in Superopolis is the best coffee?")
"Your appearance now is what we call residual self image. It is the mental projection of your digital self."
Morpheus, The Matrix
In most cases, sentinels will appear as they wish to, a luxury for those who might have to body-swap randomly and often. For the most part, the sentinel's subconscious image is respected but the system may help the avatars 'fit in' better. The Alien Raider nook is particularly notorious for putting sentinel avatars into bad 70's outfits and hairstyles (but were there really any good outfits and hairstyles back then), psychic powers and high-tech represented by pyramid crystals and wood-and-chrome gadgets.
Once a virtual HQ is agreed upon by a cell, the HQ is forked for each remote location (generally those separated by so much distance there is too much latency) and merged later if necessary. As the HQ skin is just psychological fluff, merging is generally not necessary.
So my question to readers is, what kinds of virtual headquarters would you use in your campaign? Thanks in advance...