I also am enjoying the ambience of this picture. The colours are great and you've captured that magical-shojo-twilight atmosphere.
I agree with Merino regarding the use of dither. The place you've used it to best effect is in the interior of the moon, where the dither looks like it's communicating its uneven surface, and is used with enough variety and in small enough areas to avoid blanketing together into a pattern when you look at it. I think what you've done with the clouds also has merits to it, but in the other places I don't think there is adequate reason to go to dither--it's only adding noise to the picture.
Sweet designs, I want to see more!
I love this! Especially the moon and the stars! Perhaps, this would look more beautiful if there are more kinds of dithers, some thick parts and some light parts (does it make sense?? I don't know how to say this in English...).
Thank you for the thoughtful reply, and the encouragement.