Hi! this is pretty neat! And I also like to be able to create that "colossal" sensation. For me I think it's mainly the atmosphere scattering that did the job, but it's generally hard to paint low contrast stuff, so I'm also still practising that. For example this figure could use just a silhouette and definitely not that dark in those regions. What I found out is that atmosphere scattered brightness can be roughly represented in such a simple graph (well I just drew it... could use a bit elaborate description later lol). Note that there's artistic choices also inside this relatively physical thing, that is "lit and dark region can approach the neutral point at different speed". In my diagram there are two rows of possible results at very far distance. You could use that effect to only show light or shadow shapes in certain conditions, and sometimes that's very interesting. Also note that atmosphere is denser towards the ground so the "clamping" happens "steeper/quicker" towards the bottom, and your image actually depict that quite nicely.

Hey Antti, I like this idea, pretty cool. I think what you have is usable, it's just not very dynamic (which is fine if that's what your going for). One of the tools we have as artists that can help us draw fantastic things is perspective. Changing the perspective, or forcing the perspective, can help us really get an idea across. I did a quick sketch of the way I would do it using 3 point perspective so as to really add some drama. I hope it helps you expand the way you work out your compositions in the future :)