@sunshine: it was unintentional, but since Reisen's (large girl) eyes are supposed to cause madness, looking manic also works.
@J. St.C. Patrick: Rather than using a simple two tone approach, I used a total of 8 tones per color. I wanted to get 2 effects: gentler transition between the highlight and shadows as opposed to cel-shading like the first pic, and a pseudo brush-stroke look (still don't have a tablet, and making brush strokes with a mouse makes my wrist hurt after a few minutes).
Basically, something that looks like this:

without having to get an actual paint emulation program like Painter, getting a tablet, or giving myself carpal tunnel syndrome.
What I used to try was to smudge the colors together. That didn't work well because the smudging made the colors run together. So what I did was do the entire picture in black and white, smudge that, and then block off parts of the body and then apply a curves function to each block.
I think parts like the legs look like what I was aiming for, but the rest not so much. Sharp corners in clothing are especially difficult to do properly, and in that pic it looks like I just gave up on the skirt.
As far as I can tell, Shio is an original character by the organizers of kamicon.