I think it could be really nice if you could apply some kind of comic book filter to it, maybe do some photoshop thingy, and/or render a thin pencil stroke outlines of the characters as well to give them that comic book look. 

Here are some examples for some inspiration.

Here i think the shading are really nice, especially the background which gives a very nice comic style look.

 

Also have a really nice comic look to it, and the texture are very smooth with some rough shadows.

Again the shading looks really nice with few gradient levels that give the comic look and again the blurred background is really nice.

Here i think the contrast really looks nice and again the very blurry, handpaint looking background give it a good comic look.

And if you are looking for something that is not 100% realistic but with a lot more details. And in general a quite dirty image, which give a really cool comic effect i think.

If you want to save some time with textures, colors etc and just work with grayscale it can be really cool as well i think.

But think there are a lot of good inspiration in these images, that can be used to make some really nice comic book styles, and think at least some of the styles could be copied using poser and photoshop or Gimp etc.