This is the Critique section of Pixelation. If your main purpose is to share your work, then the better place is the Daily Sketch thread in General Discussion, or a gallery website such as PixelJoint.
With larger images like this, anatomy matters a lot. Nearly all the issues I see in this piece stem from not understanding anatomy - how body parts are shaped in 3D, how they connect, their relative proportions, and you will easily see these issues yourself after some anatomy practice. You should do some studies, starting with general proportions. I recommend doing them in pencil or some other "HD" medium, as it's quicker, easier, and less prone to distortions from the limitations of pixel art. It's much easier to simplify things for pixel art and stylisation once you understand the thing you're drawing.
There are a lot of resources online for learning to draw human anatomy, and I'm not sure which to recommend because I don't know how you like to learn.
This Understanding Anatomy series of tutorials should be a good start, and draws from many of the common drawing manuals. The links to the later parts are in the description, and some of the descriptions include links to other resources. Some of the muscle/bone diagrams will probably look intimidating, but don't worry about memorising them - you just need to have a general idea of what's underneath the skin to draw believable-looking anatomy. You can learn the details if/when you decide to push your art further later.
