I'm back - not harping or making fun - just want you to understand that - the shapes used in the images are the clean basic primary shapes which adds to what you referred to as the "cartoonish" look.

You can make more elaborate constructions and props in Max or Carrara and import them into Vue for assembly, atmo, lighting, and rendering.

That would also help a great deal towards the more realistic look you're going for.

I've also been struggling for a while to create a convincing cave but my problems come from the stalagtite and stalagmites looking real or not. Just haven't gotten the hang of creating them in Vue so I'm going to give it a shot in XSI or C4D.
-Lew ;-)