I think two-colour shading's fine for now, myself. You (Rosier) still have plenty you can still learn without complicating things. For example, the contrast levels are rather low, and using two colours is a great way to build confidence with that. If you can get to the point where you can confidently use only a light and a dark colour to shade, adding more colours for a smoother transition will feel very easy, and you'll be able to focus on perfecting pixel-level stuff instead of juggling that with learning colour.
In addition, you're still shading a bit like pillow-shading in many cases, and even when you're not, there isn't a strong sense of light direction, and I'm not sure the forms you're conveying with the shadows are what you mean. For example, the first girl's shape suggests she has a thin waist and a flat stomach, but the shadows suggest a round belly, and on the latest one, your shadows suggest all kinds of dips on her thighs.

I know anatomy's been your focus, and I guess the fact that my critique all has to do with your shadows means you've been getting better at that (assuming you're learning from DesignDoll and not just copying what it spits out, anyway xP).

I think the fact that there's a well-lit column on the outside of the building right where it cuts off is what makes the cutaway not read like a cutaway. None of those columns should be so well-lit.

Grass IRL is noisy, but this is where stylization comes in - humans rarely think of (consciously perceive) objects the way they are, and simplified grass will often read more like [grass] than something that reflects attributes of grass that people don't tend to think about, like the fact that it's noisy.
Overall, I think a clear, effective image is more important than realism, especially in pixel art. In addition, having "realistic" grass in the same image as the highly stylised, simplified trees and ruins just looks odd. I think cleaning up the grass would be best. You can still make it look long and textured without making it noisy.

Seconding Achrileg. There is no "rule" for how much space a character takes up, and the professional thing is to ask. Usually employers provide style examples to guide you, and if they haven't done that, you should ask if they have any such examples for you.
It's possible that they want you to make these decisions, in which case just go with what you think looks good and fits well with the rest of the assets.

The village looks nice, but there are a couple of issues that might be making the combination not work:

The sprites are side-view, but the village is 3/4 view. No easy remedy there.
The should be a background, but it has more contrast than the character sprite, so the sprite is difficult to read in comparison. Toning down the village's contrast and boosting the contrast on the character should help.