I can't pretend to approach Dr. Geep's expertise, but I thought I'd mention a few other ways to produce toon images with Poser that you may want to try.

1.  Go into the material room and change your materials into toon materials.  In Poser 6 you do this by hitting the "toon material" wacro button on the right (hold down shift while clicking to convert all the material zones at once).  This will set the material zones to a toon style.  You can then render your image with the "toon line" option checked in your render options.

A few warnings with this method:  (a) unless you want black lines between every material zone, you'll have to change the toon id number by going into the advanced properties.  If you don't want a black line between two material zones, set the toon id to the same number.  If you do want the line (between a shirt and forearm, for example), make sure the numbers are different; (b) render larger than the preview window as even the "thin" toon line is too thick at this size; (c) reduce your lighting to 1 or 2 white or grey lights; (d) realize that Poser will ignore transparencies in this mode, so if you want transparency maps for your hair or clothing you'll have to try something else; (e) if you're comfortable with the material room, experiment with adjusting the light & dark color, line spread, and specular color values.

2.  Find some toon shaders and apply them in the material room.  There are several free sets available if you root around, and there are also various commercial packages available here and elsewhere.

3.  Render normally, export the result, and then use another program like Photoshop to convert your render to a toon look. 

I use Poser 6, but I'd imagine that all the methods above are available in Poser 5 as well since the material room is similar.  Good luck!