We are using a very simple BPR render. Each artist may slightly tweak them but here is the basic set up.
1. The polypainted sculpts are rendered using the skinshade4 material.
2. The position of the light is moved to create the desired lighting and mood.
3. The Strength of the shadow is increased in the BPR menu.
4. The Blur is decreased slightly around 1-3 in the BPR menu.
Once the image is rendering it is taken into Photoshop to adjust colors, add noise, a vignette, and a border.
It's simple but effective. Hope this helps!