I love this mini...have a diorama built with this guy in the center. He's the only part painted! ...and I built the thing four years ago...
Skin tones on yours are brilliant! His belly has an awesome translucency to it, lots of color in there. Love it.
As for more interest...I always thought of his "pebbles," the bumps on his legs and back, as more like freckles, in a way...You've brought the pale belly color around to the pebbles, but I'd have gone with a completely different color (the version I've painted has very similar skintones, and his pebbles are a very yellowish brown). If you aren't going for LotR canon, his pebbles could actually be stones, and you can gem-stone it up a bit (though that loses some of the realism).
My last suggestion is for his eyes: yes, they're tiny, but see if you can't brighten them up a bit...show us those tiny, piggish corneas! You've managed to shade his brow-ridge beautifully, giving him a really nice "hulk smash" feel, but his eyes are so dark they almost look closed. Alternatively, you could take the dark even farther; living in a cave, he'd likely have permanently dilated pupils. But even with big pupils, I feel like he'd have "cat's eye" reflectivity going on in any light bright enough for him to be seen.
Again, your skintones are jaw-dropping. Thanks for sharing!
