I'm a total newbie, so I'm sure this idea is not original, but I stumbled on this technique for getting a flatter toon-like look for a Poser render.

Using your favorite image editor:

• Step 1: Turn you Poser toon render into a greyscale image.
• Step 2: Posterize the greyscale (I like 4 levels)
• Step 3: By hand using the color replacer tool, replace each of the four shades of grey with a color from a fixed limited palette of colors. I keep my palette as an open image that I can grab colors from as I need them.

Of course you use different colors for a given grey depending on whether it's skin or clothing or hair, etc. SO each grey might become any one of several different colors in different parts of the image. But with the color replacer it goes really quickly.

With this technique you don't get those awful colors you get when you posterize a color image, AND you get to use precisely the colors you want for a given piece of work, giving you a unified palette.

I'd love to hear about other, more experienced people's tooning techniques.