oh man...those clouds are GOOD

Mmm, the bottom contrasts a bit though, but that may be quality issues

, and when you render out on max it should be good

Also, the bottom low lying clouds you should make foggier like the clouds above-that'd be awesome then

And if you used grass particles/models near the end, where there is low lying cloud, that'd give it a more 'rougher, detailed' look.
Great job! I was really impressed with the clouds!