It's been a while since I played with CC3, but it looks as though the cave walls sheet has two effects applied: The first is an inner glow with a dark color. The second looks like a bevel to me, but the shading is very subtle. It might also simply be an outer glow with a very low feather value and a moderate spread, causing it to push out from the wall, then end abruptly.

The sheet effects can be very powerful, but don't go crazy with them because as I recall they could be quite slow. Also, their appearance depends on the resolution of your image, so if you export at two different sizes, the sheet effects may not look the same on each one.