I think caves can fit into one of three categories:
1. A plain ol' cave - this is defined as being an old waterway that was carved over thousands of years by erosion and has now been moved geographically above the water table.
2. Mines - defined as a subterranean network of paths dug by an intelligent species for the purpose of removing ore. These types of caves in TMW could be dressed up with additional tiles depicting leftover ore, old tools, wooden support beams, rails, and carts. Straighter paths would make sense in this type of cave.
3. Cave dwellings - whether they were created by natural forces or intentionally by some being, this category of cave is defined by having elements and signs of intelligent life. Our tilesets have some of this already, but the following could be added as more options: torch holders (facing east, west, and south), large stone tile floor pieces, a stone pedestal for ceremonial or other purposes, fire pits, and sarcaphagi for tombs and catacomb type settings.
Some pics for inspiration:
Sarcaphagi:



Catacombs:



Torches:


