Sounds that would be good to have...
-Menu sounds (cursor moving, canceling, selecting, etc)
-Monster type sounds (growls, grunts, etc)
-Things that you'd hear in silence (crickets, wind, anything you can think of)
-Water (drip, stream, waterfall, anything else you can think of)
- Lava (the bubbles and whatnot)
I can't think of anything else at the moment