Well I decided to do an edit about what could be done with your first image.
I think overall the shading on it was really random and messy. You don't have a constant lightsource and it looks as though you just scribbled different shades around. I know my edit isn't really great as I'm not good at shading either, but it does show something more constant. I also think the outline is a bit stiff, but I didn't change any of that. It really has no pose, it doesn't show any depth of the character, or anything else to make it stand out. I also think, out of the few colours to do with this, the ones you picked were a bit off so I changed those a bit, I added just a bit of saturation to the greys.