Since you mentioned cartoon with lines, if you want to get tricky, save both versions and go into Photoshop. If you put the cartoon render on top of the toon shade render and set the layer to Multiply, you get more shading. (Other layer blending modes give interesting effects as well.)

I hope you don't mind, ernyoka, but I used your picture as an example:

The left is just toon shaded.

The middle is toon shaded on the bottom layer with the cartoon with lines render on top set to Multiply.

The last version is me getting fancy. The bottom layer is the toon render. The middle layer is cartoon with lines set to Multiply at 100% opacity with the skin on the face and arms erased out. The top layer is cartoon with lines at Multiply with 65% opacity. I think this technique more depth to the picture without muddying the face, like the middle picture did. You can get fancier still by merging the layers and using the smudge tool to make the shadows slightly smoother.

(ernyoka - If you have a problem with my using your pic as an example, please let me know and I'll take this one out and do one of my own! I'm being lazy right now.)

I already have a tutorial on cel shading with Poser 4 and Photoshop on my site. I may have to do a P5 one as well to take the toon shading into account. (http://www.fallencity.net/tut-posi/p-cel1.php)

Cheers!