You could also tell him what he could do to improve...
I also like #1 #4 #8 #9.
I like your use of 3-d shading and the cartoon look... (not really 2-d, not really 3-d, Hard to explain...) In the first one, I noticed how you made a brighter "glow" by the items in the night sky. For example, the flag sort of makes a glow in the sky. Maybe if you make the sky all 1 shade, but still have the moon glow and all that, It would probly look better (not saying it looks bad or anything).