I like it, it has a lot of character. i only notice 3 real things, all of them very minor:
1) the speed of the clouds, clouds are very slow moving, so the high speed they travel up creates a sped-up effect
2) the angles of the moon and clouds, it isn't a huge deal but it contrasts with the generally smooth line work of the foreground
3) the effect around the moon is not pixel art by strict standers (it seems like a computer generated effect)
all of these things are more preferences, than anything, tho. as a piece this functions well