I think the thing I notice the most is that it looks a little messy. The main character has a mixture of colours with a lot of the same hues with little or no separation. Also, the highlights appear somewhat random with spots of light colours on dark areas. The pants hear and shirt come to mind.
Also, the long, darks lines/clouds in the background stand out very much and could probably do with an extra colour for blending. Maybe make the whole thing lighter so it won't mix with the towers.