Your pixelling techniques are good here: good color choice and combination, nice shading and selective outlining, and pixel usage to define the character in such a size. A little pick about the colors: I'm assuming he´s wearing some sort of pants, and i suggest you use a different tone for his legs other than the one used for the skin, they look like pants made of skin
Your obvious problem here is the anatomy of the character. You should study what you can on anatomy, like the proportions of the human body and muscle groups. Practice a bit drawing from life, or from good references (real pictures or drawn ones). I suggest you spend a good time doing this on paper, and then come back to pixelling, look at this piece and see if you can work out the problems it has. Good job, and good luck!
