At first, I thought you traced over the original art. But after comparing your drawings with the originals, I think you "eyeballed" the art and then tried to imitate it? Eyeballing is a good way to start trying to draw, and you do have the right idea going on. Nothing looks really out-of-place although some parts can be proportionately better.
I miiiiight sound a bit like a black sheep compared to the earlier comments, but I say trying to precisely imitate the original splash art is a-okay at your stage. Learning anatomy and how to shade and developing your personal style are excellent topics for anyone, of course, but so is learning how to measure your subject with your eyes. Measure the width of your subject's arm compared to their head, identify how dark the shading is in their hair compared to their skin, etc. Some artists produce drawings that look exactly identical to photographs and that's fine so long as they give credit where credit's due. They learn about their subject in great depth. Measuring the original art will offer you insight about how it's composed.
That's just my two cents though. You can definitely just follow what the others were saying earlier about learning anatomy and trying new poses and such. Anatomy's always a good place to begin.
Hope you can learn a bit from this thread, Malek.
[sg-soraka]