Working on it. I had to shorten the lists by putting them in folders based on what asset file they came out of. This also told me that multiple textures and models have the same name, but exist in different asset files. Which then means that there are 10s of thousands of files to play with. 
'> 47,158 files so far, from 33 asset kits. Granted, about 1/4 of those are textures, and some of the files are fully duplicated from pack to pack. Just got to weed through them all systematically.
Anyway, I did find the "middledark" and "lava caves" files. The rest of the new content seems to be inaccessible in dungeon crawl, but I'll eventually find it in the assets. Probably got dumped in some horribly named, or shared asset file.
I can confirm that lava caves and middledark are both mods for the drow caves/bandit caves areas. They also added two more larger tile groups to the cave kits. One is called pretzel, and it has a x shape in a rectangle. You can cross the room in the middle of the x, or traverse the edges. Interesting room, but I can't seem to get it to randomly pop up EVER in the dungeon crawl. It appears to be a 6x6 NWN sized room. Another room is a long tunnel on a diagonal, with two door slots at each end. Kinda like an X stretched way out >------< on a 6x6 NWN sized room, called "skull". I also see some "balcony" rooms, which are 3x6, with the top half of the room up a level higher than the bottom half. These too do not show up randomly in the dungeon crawl for me. Other shapes include "tadpole" 3x6, and "choke" 12x12, and some corner "stairs" rooms.
Here's a few samples of the stuff I've pulled out of just the underdark descent and drow caves so far (244 unique mesh groups):
