When the assets were completed, I replaced the blocked out scene with the final objects and was able to judge how well the scene worked and how well the objects were interacting with each other. This was the moment where I could iterate on the scene's objects and clean up the composition. Dead spots were filled with objects so there weren't barren areas between the characters (Fig.06).

Fig. 06
Setting up the lighting and materials, I established a theme: dark, murky metal, with light hitting and reflecting off the mechanical materials. Lighting and color additions were going to be accomplished in Photoshop. Since I was working with mental ray, the lighting setup consist of two Directional Lights and a Skylight (Fig.07).

Fig. 07
I laid out materials that fitted and blended well with the objects they were assigned to. I did this by taking advantage of the Autodesk metal, car paint and SSS materials provided. Setting up a simple lighting setup helped me test how these materials reacted.
Slight modifications to the materials were a given. The MR SSS had to be tweaked to fit the lighting setup and metals had to be modified, so the specular and reflections had to hit right. Small resolution iterations of renders were made over and over again. As expected, to fix material and lighting issues, I rendered artifacts. This is a given most of the time (Fig.08).

Fig. 08
After going through the iterations to find and fix graphical problems, I rendered with mental ray, which provided some fast results. Overall my plan was to render nice, simple passes, and composite and paint in Photoshop. Final Gather wasn't needed; the render worked well without it and it saved time (Fig.09).

Fig. 09
Using Render Elements I was able to render my diffuse and Z-Depth passes. An AO pass and Light pass were also rendered. The following passes were rendered as a material override: rock texture and a metal texture. These two were going to be used as a paint FX pass (Fig.10).

Fig. 10
Fig.10