Wow, great concept. Good tesselation on the foreground texture. Highlights on the rocks in the far back are too light looking for the atmosphere. Maybe they need to have some pink tinge to them. Furthermore, your character lighting could suggest the use of some cooler shades for the darkest parts of those back rocks to help them blend in better.
I agree with Helm on the background. Because of the open flat shaded areas, the detailed spots are over-emphasized, and this causes any foreground objects with less texturing or inadequate contrast to look bad. So I guess the general rule that applies here is more contrast ( or contrast-by-texture ) in the foreground.
As with what Helm said about your character being too dark, I agree. Furthermore, you should consider making one color noticably lighter than the other, so that we may have a better understanding about what is meant to be the 'negative' lighting. Plus in general, that will better compose your piece. The sky is red, so I assume the red shall be the color to become lighter on the character. If you do not want to lighten your character very much, than expect to darken and remove contrast from the scenery, which means even less contrast should be applied to the sky.
I like texture of the path, though it could use maybe less contrast further 'back', so you get more of a sense of contour, and should be able to conceal that obvious horizontal line to some extent.. in fact, I'd make that your next focus. Work a bit more with the greenish looking background features and try to blend/fade-to-black to give the work a bit more of a natural look. Again, like Helm said, some grid is fine, but in lieu of all the rocky work, it might look a bit out of place.