We can't really critique your stuff until you have a basic grasp on the fundamentals of art, I really, really, suggest you stop pixelling for awhile and pick up a pencil and some paper and draw from life, draw your tree in your backyard if you want to get better at trees, etc., you will improve tenfold. Also once again, I will ask, did you use reference for your tree? Reference will help you greatly if you use it properly.