here are my tips:
1. if you dont want to have these white spots near the lineart, you can either do what birb said or use a pixel brush like i do
2. use stabilizers so your lineart isnt wonky
3. minor detail, but if you made the stars vary in size a little bit more it would be nice
feel free to pm me/post on my profile/homethread/whatever if you have any questions about the program :]