Hey this looks pretty awesome! Very nice concept and execution!
You already mentioned the mountain's surfacework could be improved. I'd try to restrict the snow a little more.
The silhouetted trees are really fine. Renderquality is very good also. Which settings did you use?
I have some suggestions:Further I'd try to lower the cloud-plane just a little little bit and try to get it more horizontal and to give it a little bit more fluffy/cumulo look.
Maybe you could also lower the sun a little and increase red sky decay to get some more yellow/orange lighting on the mountain and it's snow and probably a nice soft glow on the clouds, that'll look awesome
Maybe you could also decrease the size of the moon a little (half the size at least) because it fills up your empty sky way too much (to my personal taste of course).
It draws too much attention I think and that's a pity, because there's so much to see
I hope you understand my suggestions aren't meant to be negative, just to be of (good?) help
)
So, it's very nice image, it certainly looks "halfway decent" ;-) even better...
Martin