I've done some looking into this before when I first added the map, I wanted something that showed you where you're currently are and revealed itself as you explored rooms, rather than a map that gave you the whole layout right away. The problem with something like that is Twine 2 isn't really designed to be very graphical in nature, the only way to add even basic images at all is to break them down into base64 hex code and dump that in a special passage. And the only way for me to do what you ask within Twine's format is to have a separate image for every room to have a dot in it, and then switch what image is displayed for a map depending on which room you are currently in. Making the images would be tedious, but doable, then I would have to convert it into Base64 and each image would require its own special passage filled with a massive wall of hex code, and then set up a massive sequence of If/ElseIf macros querying whether you're in a particular room until it finds the one you're actually in and displays it.
While this would be possible, it would take an excessive amount of work, probably at minimum 2 weeks of dev time, would massively clutter the development area with a huge block of passages filled with Base64 hex code, would significantly bloat the file size (which I admit is currently tiny and probably wouldn't get problematically large, but still), and would still be ugly as sin. Plus the entire process would need to be repeated for every floor of the temple.
I don't like the current map, it's only there as a temporary measure because people really needed something to help them navigate, so doing something that would possibly require weeks of effort to entrench that ugly map deeper in the game is not at all appealing. Twine 2 does accept javascript and HTML so I would much rather make a proper map system that way, the problem being that I am neither a Java nor a HTML coder.
I was going to take some time to look into it more once the first floor was complete, which is probably two or three updates away.
TL;DR: I don't feel like putting in a huge amount of effort making the current slapdash map slightly better, and would much rather invest the time replacing it with something superior once the first floor is fleshed out.