A set of crystal cave graphics with a matching BG on layer 3.
The FG includes animated lava. It also includes a lava glow for use on translucent layer 2, and the crystals work well on translucent layer 2.
There is a less crystally variant of the FG (using the same map16 and everything), in case crystals aren't your jam re: caves, but it is less featured than the crystal version. In particular, the BG is only available in crystal flavor.