I'm gonna start with the eyes, mouth, shell hair, which are well-drawn. There is no need to change those sections.
However, this PNG pic has little or no special attributes whatsoever. It would be smart to add many additional, minor objects to this pic. The back-ground, for example, could use a background of the beach and sea with some boats and surfurs, instead of a total red wallpaper.
On another view, the connection of the hands are not realistic. You can basically see the difference. The arms seem very unrealistic. I've never saw anyone with his/her upper arm slimmer than his/her lower arm. You should make them at LEAST the same size (in this condition, make the upper arm fatter/bigger). Also, adding muscles for the upper arms would be a good choice, since he says something related to a sport. Also, the colors are different. Convert the arm color into the normal body color.
Last, this turtle's torso and stomach seem extremely unreal. Re-construct it into a form that are equal to both sides, so you can have a good shaped torso and stomach. The stomach could also use some ABS (six-packs).
For the rest, good. A 2 star for this.
--The Review Request Club.