Hi, this looks nice! I like it.
One thing I think is worth looking at is the difference in the amount of colors you use for the moon vs the buildings.
With such a small resolution, you are able to get the effect you want with few colors for the buildings. But for the moon, which uses a lot of colors (comparatively), I think you are actually less successful in creating a nice effect--I would suggest trying to redo the moon with 2 or 3 colors, but with more contrast between each shade. Don't be afraid to use a photo of the moon as a reference!.