Gorgeous! The lava effect is really nice*1*. Must be a really magical land, what with the snow not melting merely feet from the magma flow!
I like that you included some variation in the snow terrain's colors, the gray-white fade, that is. Works really well. Might be nice to see some dark grey/bley or dark brown mixed in with the black terrain, just to give it a little more character. Or perhaps incorporate it into the tower. Maybe even just at the base of the spire, to distinguish between the land and the structure. But even if you don't change anything, I love it!
Do you, by any chance, live in Minnesota? I had to spend a night there in August as a result of a flight delay, and checked out the Mall of America the next day while waiting for my flight. I checked out the PaB wall in the LEGO store there, and just *had* to take a picture of this, because, well, come on: Cheddar Cheese!
Wanted to grab a cup of them, but my luggage was already well past the point of being over-packed. Now, seeing your MOC, I really wish I'd bought a cup and found a way to fit it. Seriously, lovely terrain! haha