I like it so far. There is just one thing i'd like to add that you might consider.....
Select your whole scene and group it, and then enlarge the whole scene. IMO the distant haze looks so more realistic. experiment with the size and do quick renders to see the result.
Also a little more glow from the lava. Raise the opacity of the mat and place a radial light source just underneath the surface. You may have to experiment a little getting the opacity right. Of course this would work better with volumetric world turned on, but will significantly slow down your renders....even in quick mode LOL, but it would be worth it. Good luck! :-)