Taking the Nightcrawler 2D assignment as an example here's how you can approach a" figure with strange anatomy and dramatic pose/lighting" scenario. Sketch out your ideas first of course, but when you have a good idea where you're heading you can create your own custom reference in a 3D package for proportion/perspective/lighting/composition/inspiration. Not to slavishly follow it you understand, a painter should always try and inject their artistic vision and character into a piece - just use this as one more tool to help make your art more polished and professional.
I knocked this up with a biped (scaled and adjusted to be a bit Nightcrawler ish) and some boxes in 3ds Max, played around with the pose and a couple of lights and cameras for a bit, it didn't take too long.
Damn, I wish there'd been 3D packages when I was painting comics, all I had was plasticene. Sob...