SuperShot was mentioned. That should be helpful especially because you can script it, for example via LogicBricks. So you can easily take screenshots from the exact same positions, make slight scene modifications and repeat. If each image for your comic is setup as a subscene, you could even automate loading the subscenes and taking the shots. So, you can easily make modifications and redo your screenshots in seconds or minutes. For example, you realize 100 screenshots into your comic novel that you would have needed to place item X, say a dildo on the bed in the background. Redoing 100 screenshots by hand can take a while. Of course it needs clever setup of how you store your scenes.
You could also try using PostMagic with a Toon UserLUT. That's simply a reduced color palette, which gives you a somewhat cartoon'ish look. Probably not what you want, but worth a try

These two LUTs come with the plugin, but you can easily make your own LUTs: