maps and walkthrough for every area can be found here: http://www.angelfire.com/games3/ShadowTower/
additional snippets of maps can be seen here, including the official 3D map of shadow tower region that used to be hosted on from software's ST page: http://imgur.com/a/W0eWW
going forward, i hope to acquire some of the japanese guidebooks for the game, from which the other imgur scans were pulled. if i can do so, i'll make hi-res scans of the maps
i have the guidebooks. they have quite a few interesting bits, but i don't have any way to scan them as of yet. will update this thread when i know more.
additional maps are found in the completionist's guide:
https://docs.google.com/document/d/1G9Wu-NHmm0wnMqiypGtXSHzcgbLy_tg4s9yJc7qhtH8/edit#
spawn zone maps in japanese: