are the sparkles reflections from crystals/gems embedded in the rock, or magic sparkles of some kind?
if the sparkles are reflections from crystals/gems, you need to make sure they are not occurring too far back into the darkess, where they would not actually receive any light. If they are actually lightsources (as opposed to reflections) then you might need to render this emitted light onto the surrounding or adjacent rock.
if the exit to the cave is to outside, or safety (which it maybe if welcoming people into the website?) try some warmer yellow tones from outside. You will notice this technique in movies also, less color & bluish tints = non home like, yellowish warm tints = comfortable/homey. definately go with the edge glow on the characters.