Coming to think about it, I think he's referring to the custom level called "Tower" that I've mentioned, as that used the temple tileset.
Great! I'd been doing a little digging too and this confirms a what I was tentatively guessing. See I found a copy of version 99.9b in a neglected corner of my HD, which included the tower levels, but also some levels that were clearly downloaded separately.
Is anybody else interested in playing this level set? I'm not sure exactly who made it (author is listed as "FIFTH"), but I doubt they'd mind if I reposted it.