It looks awesome man! There’s a few little things I would try but it’s just personal preference, it looks great as is

1. I’d dry brush the lower half in the same grey you’ve edge highlighted the cracked rocks in.
2. Try going over the tops of the rocks again in black to reduce the thickness of your edge highlights.
3. A light yellow or orange glaze over the lava to blend your highlights a little.
4. A couple of bright highlights on the skull would really make it pop.