Hm, you're on Poser 11 which is two versions behind...the earliest I used full HDRI on background was Poser 12 with this shader from Freestuff:
https://www.renderosity.com/freestuff/items/90149/background-shader

You definitely need some sort of dome or environment around your scene, right now I don't see anything. You may start by using EZDome (Poser 11 version) from here:

https://cobrablade.net/snarlygribbly/poser.html

Also, absolutely as hborre says, if you do comic style rendering, simplifying shaders by stripping out ambient glow and any Firefly 'cheats' will be equally important to how you light. In Superfly in general, less is more, especially one you introduce a dome or background HDRI to light the scene (this may or may not work for you as you're doing comic style). Experimentation is the key, but only change ONE variable at a time so you can track (this is crucial). Lots of test renders.