Well I am just going based on your reference drawing, but the hands and feet look like they just need to be a little bit larger. Also, the upper chest looks a little more muscular in the reference drawing also, but I do not know what you are going for. Otherwise that, keep up the good work so far!

~CGPMaya84 (also DragonTU84 from SimplyPhotoshop and CPAnimate84 from SimplyMax)