Super map - I haven't realised that Torston had a tutorial - I'm going to try it myself one day.

Without knowing what you are aiming for, my advice would be:
-Your snow looks great, however the transition between the cave insides and the snow is too sharp - you need to merge these a bit more and your snow will look more realistic.
-You are right - the shadows on your steps are off. I think this is for two reasons: 1) the shadows around the pillars are too dark relative to the other shadows in the room - increase the contrast of the step shadows to match & 2) the size of the shadow between each of the large platforms should be double the size of the shadows between each smaller step. Does that make sense? At the moment, your shadows are the same regardless of the drop, but in fact a larger drop should have twice as much shadow.
-You might consider increasing the contrast slightly between the wall shadows and the cavern floor - the shadows in general are rather subtle.

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EDIT: Ok I checked Torstan's map by following your link and am even more impressed by your work! Torstan's snow is superb and you are very brave to try and copy it exactly. Your current snow is fine once you bring it inside the cavern a little like he does. In the places where you bring the snow into the cavern make sure to have blue wall shadows. Look closely at his shadows along the steps, though, and you'll see what I meant above. Good work.