I can tell there's a lot of work into every single one of these pictures, and I love that; however, it seems like you're putting 70% of the work onto making squigly lines for the shades. In some sections, it looks really good, but in others, it feels needless and sometimes even superfluous, aside from consuming time that should probably be spent working out the anatomy and expression better. There's a serious lack of emotion in a few of these, and even if the rendering is top notch, a picture that is afraid of showing itself really goes nowhere. Unless the guidelines actually demand that the symbols featured ARE, in fact, lacking in emotion, try to spend the time and energy that you'd put into overdoing the lineart into making really getting the feeling across with some serious expression and polishing your style to really show how much of yourself you're putting into each picture. I know that in magazines or comissions, this tends to be the biggest obstacle, but it's something that is really necessary to make a picture look great.
It's more about the subtle things going into the image (like a slight smirk, or some wrinkles) that tend to get a message across more.