Hello Friend of Trolls
I came to show appreciaten for your concepts, I really like them and see potential!
As said above, to attempt big sprites as a starter at pixelart is kind of tricky and troublesome to get things looking alright! The very most important thing is the concept and to imagine as many details as possible so your image doesn't look that blank (depends if you prefer a more comic look with less details or one style that has more physical rules applied to it)
Now to the trolling-around:
I will still showcase on what you could do with your rather big sprites, since it is still useful for portaits or closeup things! (I really suggest not to make spritesheets this big, as it is very very time-consuming (I'm one to talk))
What I did here in the first step was sketching out the rough idea I saw in your concepts combined with my knowledge of anatomy and perspective and some lighting-enhancement through thicker defined/sketched areas that imply shadows.
I then blocked out basic colors behind the lineart, and selected the lineart itself to change its color according to the bodyparts so the outline isnt just black and merges with the object itself! Everything from that point onward is detail and polishing (application of various pixelart techniques such as AA/Dithering and whatsoever) until you are satisfied with your result!
