Looking back, I should've let it be. I did a quick spray of orange to try to tighten the pencil work, and it ended up muting it a bit too much. Doing a quick pass with the pencils to bring it back out ended up just muddying up even more, and also losing the likenesses a bit as well, so I just stopped.
It doesn't get the 'FAIL' however; since this is intended to be a learning process for me, I did get a lot of ideas to approach this differently. The rendering technique is good enough for a certain level, comic interiors, smaller portraits (Leia's face is about 3 1/2" high, Han's 4") and mistakes nonwithstanding, I think the next batch of these smaller images will be even better.
Overall, the drawing was strong, and I was really happy with the underpainting on this one, the rendering has been a bit of a problem for me; it gets muddy, as I'm still a little too heavy handed, I need to keep working on people and drapery - the more organic stuff. Since I've been working digitally on robots and vehicles for the last two years straight, (almost exclusively!) I'm losing my touch - I need to keep up on the softer side of life!
The plan will be for quite a bit more drawing the facial forms with the color pencils along with the heavy black pencil. When I did the underpainting, it help so much in defining the curves of the face - trying to emphasize that with the pencils on top got so muddy, it lost most of the subtlety. Next time I'll try to keep the post-paint pencil work to just the structure of the face, eyes, nose, mouth, and jawline, and see how that turns out.