I've been playing around with an idea for a minute of something similar to what Rack has in canon. A demon that feeds off (others) sexual energy that senses when people are "in need" and the room supplies that for them, moving locations based on where it's needed most. 

You can play around with whether the demon working as the "secretary/owner" is more evil, neutral, or nice/helpful, but I've played around with it also being a time chamber of sorts and putting it in season 6 to give Buffy a sort of break. Any season would work for that though cause honestly, when does Buffy NOT need a break? Like, a day in the room would be a few hours (or even less) in real time, etc. This way, Buffy would not be pressed/have the excuse about staying away from Dawn for longer periods.

Room stock options can be played with as much as you prefer, including amenities for humans (including food, a tub, perhaps, etc), or objects to play around with. Are these provided upon request, or are they just there, taunting them, out in the open?

The rules I have set up for my own idea are that the demon owner is more helpful and deals in more convenience and consent, and they work as a secretary of sorts, bookkeeping in a room before checking them in like it's a hotel (just because they enjoy the process). Depending on fic author and intention, this can be played around with. Perhaps they have hidden motives because the Slayer dropped into their business, they're not a secretary and they just watch the room move without speaking to clients, etc. Just figured if anyone needed a locale that fit into most scenarios I'd offer this one up. 

MUST HAVE:

HEA/HFN

Spuffy

Room main rule MUST be that it responds to sexual tension. Whether it is the room itself or the demon/owner “steering” the room is optional

CAN HAVE:

Angst

Hurt/Comfort

Claim

Spike has prior knowledge of the room existing (or he’s just as surprised as Buffy!)

NC-17 Rating is optional

MUST NOT HAVE:

Threesomes

Demon/Owner does not participate in room activities

For must not haves–you can still use the idea, but it doesn’t have to be a challenge response!