First I have to make you compliments for your work and your attempt to get feedback for it. Not everybody does that. So here comes my feedback.
I really do like your character. You managed to transport a certain mood to your figure. So this is pretty believable.
I would like to see more detailed parts. Some aspects of your character are completely undefined and I can´t figure out, what they are supposed to be. Take his weapon (or stick) for example or his red beard. Even if you just indicate form or texture it would benefit your character concept a lot. Since it is a character concept peace every aspect of your turtle needs to be clear to the viewer.
And as the others mentioned before you should learn more about values and light. I would recommend you to take your painting and redo it just with gray values. After that you can apply color to it.
