There's a couple issues here.
-Need more contrast. The colors are really similar and it makes him look really flat, especially on the face where the only readable features are his eyes.
-One arm is longer than the other one. I realise the perspective you are trying to do but the pixel offset is too big. It should only be 1-2 pixels above his right arm (our left)
-his arms are squiggly, and not anatomy based. There is no visable distinction between hand, wrist, bicep, and triceps.
-I think his pelvis may be sticking out too much. I would shift the bottom torso to the begging on his legs left 1 pixel.
-You have 2 colors for the outlines but they seem to be used randomly and aren't different enough to justify the use of an extra color.