@zzhou, welcome to the forum!
Your office palace has many parts to it in my opinion. There’s the background of your office of course. That’s what gives it and whatever you store inside it potential for creating memorable images.
The next part of the structure is the subjects, items, or locations you select which you could call keywords that lead you to whatever you store there. In your case, you want to identify locations so that you can visit each one of them in order. If you only cared about the stored image and its associated information, you wouldn’t need the palace.
The last main part of a scaffolding type structure that holds images to understand is the the way you get around in it among all those keywords. That’s the sequence or traversal method and can be a rule like a number as you mentioned, or it could be a narrative where one keyword image follows another for something you may do in your office regularly and know well. I often alphabetize my areas. Sometimes I use both to help reinforce my ability to remember it. Now you can go forwards and backwards in the images stored there.
So, if you have 27 areas, you must have a very large office! Areas in a background need to be spaced out so that they don’t overlap easily usually. In my office, I would use the area around my main desk, the area around the printer desk, the wall where I have my bookshelves, the area where I enter the office, the area of the wall in front of me, the area of the floor, and then I run out of areas. Maybe the ceiling if I had to add one more would work. I usually max out locations after about ten. If I wanted to assign images to objects around my office, I could find a hundred though.
Do you have something you would like to memorize that requires 27 or less images?