The perspective in the backround is way wiggy. @ @ It's gonna make me seasick! I think it's how the banister and the horizon match up-it's a harsh slant, but will isn't tilted with it. There's more I could say about this if you want...
As far as detail goes, his left hand looks very unconvincing. At this angle the hand can't lend much imagination to the drawing. It's flat, straight on, and looks slightly uncomfortable-which leads up to the angle of the shoulders. The entire body, from the boots to the chest, is turned towards the rail. But his shoulders and head face straight on, making the neck and upper arms looked strained. The pose would be acceptable if his torso was turned farther to the right or his head was placed more to the left. On the linart, the inking is very clean. In the sleeve of his left arm there are darker lines for the creases right? Continue this along the lines of other creases, and it will give the cloth more form and depth.
Lets start with a background... At first I thought it was stairs actually. But then I saw the sealine. First of all, the sealine usually is straight, unless there is a mounty land close to us. And its not exactly horizontal - did you mean that he is standing on a ship which is tilting?
Then the ... deck? It seems you didn't finish it properly First - you should erase unnecessary lines so they won't look transparent. Second - there should be kinda... ovals or so at the base of balusters so that we could see their form. And I do not understand why you applied shadows on them - the rest of the pic is just outlines with no shadows.
Then the perspective - it is wrong. You should never forget about laws of pespective when drawing, especcialy with a background. I think you know them, ust was careless not to apply ) The main mistake about pespective is that the character and the background are drawn from different points of view.
Next - just an advice - never use a ruler to draw straight lines. Learning to draw straight lines yourself trains your eye and hands. It is kind of practice - when you'll be able to control your hands completely your drawing skill go way up.
Now lets look at the character.
A mistake with his head - the face is drawn as if you are standing exactly in front of him. But there is a bit more amount of hair visible on the riht - as if the head is turned slightly. These two facts absolutely do not match.
Then from the neck down to his knees everything is well if we suggest that we are looking at him while standing just in front of him (this fact doesn't match with the banister, remember?) but then you tried to put his arm on the banister, and thus there is a feeling that something is wrong with it. Same goes with his feet.
You've also missed some folds on his clothes.
I guess that should be enough) So, you see, the main advice is not to forget the perspective)
(PS - I'm not a master in drawing so I probably was wrong with something - I just said my point of view)