I say the colours need more harmonising, particularly the greens on the hill. At the moment they're very distracting and lead the eye away from the figure. My suggestion: get more blues into the hill and bring more saturation and oranges into the man. Sky is dull and feels like it washes out the piece. Lighten it up, maybe even add a touch more saturation.
A few little jaggies in the dim clouds outlines. AA on the branch is kind of banding, maybe find another tone to add to the AA?
Shading on the hill doesn't really make sense paired with the silhouette. Doesn't seem to fit the implied volume. Treat the hill more like an actual solid and shade in accordance. Maybe give the hill some slight texture as well? Just an idea.
Feels like more could be done with the subject. If it's king of the hill, why not give the guy a bit more of an expression on his face, maybe a competitive glare, or a slightly primitive-man face structure?
Give more of a sense of perspective to the background. You have aerial perspective, yes, but the way you have the nearer plan going up over the far plane (mainly on left) in a couple of places works a little to break that sense of distance.
Possibly give more dynamic to the distribution of features in the background. Have sections of negative space (such as the majority of the top left corner), then balance a pack of clouds against a mountain cluster on either side of that and the subject. Maybe even add a sun. Just ideas to bring more visual interest to the composition, everything feels very even in the background at the moment and it kind of makes the eye just skim it.
Looking forward to seeing more
