What I generally miss so far in all the entries is a plan.
For challenges like this I would collect references and basic research to choose what I would like to make and especially which type of scene would suit my TG strengths best(!).
I think that's very important to have before getting started.
Then it's a matter of iteration and I know you're very good at that, because you've proven before you're not afraid to keep working on a scene to nail it.
This image is already very detailed and "busy". Snow, jagged/rugged mountains, dead tree, wild sky and an erupting volcano. Not to mention the ice shelves.
It's ambitious, to say the least
but may be you should take a step or two back and first think about what you really want, instead of everything possible?
I think the best Iceland pieces are the ones of simplicity and tranquile almost desolate atmosphere.
What do you think?