So going along the lines of 'Elements' that you can add to a typical, cavernous encounter I started wondering what I could toss into these maps to make them interesting.

So I started a list:

Lava Flow (from Torstan's original tutorial)
Water (pool of some kind)
Pit / Chasm
Slime (either large sections of it covering the tunnels or a chamber.
Moss / Lichen (something green and carpet-y that they will have to walk through)
Webs (though I have almost no idea how to simulate this for a cave floor)
...

And that's when I kind of drew a blank.

Anyone else have ideas?