I'll have to disagree on most of your points, Werewolf.

-The background is fine, if you follow the mountain line you will see that it goes outside the frame well before it reaches the edge of the prince. Perhaps it's unrealistic to have a city on the left and a mountain on the right, but it's not impossible.
-I agree that there could be more shading, however it does have some.
-His coloring choices are fine, except the sun.
-With the amount of circles and curves that the prince has, I don't think it would look as good in 2x1.
-Negative space ain't bad, and it's well used in this piece.
-There are a few imperfections in the lines.
Also, wtf? What does this have to do with that C64 banner you were making? The only similarity I can see is the palette.