Trying to finish this piece but not sure how...

[ChantalFournier]

I think this is a strong thumbnail. If it was my piece, I would want to show what the heck he's doing there. Is he leaning there because he's injured? Is he trying to intimidate something in the dark coz he's coming to get it? What is the action? Ideally, there would be something in the vast dark area, maybe something very subtle, like someone waiting in ambush, we can see it, but he can't, or the object he's looking for. The step after that would be to gather references. Mostly rocks and pictures of you or someone you know in pyjamas leaning on something while being lit from behind.

Then I would start working on a clean drawing, making sure I have the right size and proportions of canvas, then drawing the anatomy as accurately as possible, then adding clothes. I would design the rocks to have interesting negative shapes. Then I would either do some color comps or start rendering in b&w.

So basically, what you have here is a good idea for an illustration, but it's far from being ready for a render stage.