I had a judge at an art contest two years ago tell me the same thing. xD It is actually very good advice, though, and I thank you for reminding me. This was back in Art I days, when I didn't pay much attention to composition. Wow, that was a long time ago... xD It's good to hear this kind of thing from someone who's not an old fart of an art teacher. ^_____^ Thanks again.
Whew! glad that my opinion match up with a professional's. I think the composition is fine though, just the shades/contrasts and the moon's shape. Well, some art teachers do tend to be closer to being teachers than actual artists, but you know, they have their qualifications.