Creating the textures was done in two stages; drawing the basics with PolyPaint and adding details in Photoshop.
In PolyPaint, I drew a texture over the model in ZBrush its main parts and outlines. In Photoshop, I improved the quality of the texture and added detail. The texture for the bump was made of high-poly models in multi-map exporter (ZBrush plug-in).
There were some exceptions, for example: the texture of the ground. I made it from photographic references and made them seamless. Creating seamless textures is not difficult. I'll show you on my avatar below.
Duplicate and reflect the texture vertically, cutting off the edge and taking away the seam (paint over). Repeat the same steps with horizontal reflection. Now its a seamless texture.
Thus, I was able to get a texture of a dirty ground.
The ground texture I used
The bump map just a black-and-white version of the texture. Best results can be achieved using a program like CrazyBump
In work such as this, there is no reason to make complex lighting. The only thing I needed was a simple light with clear shadows. This lamp was V-Ray Sun.
The lighting after applying the V-Ray Sun
These were also simple enough you can see the settings I used in the screenshot.
Settings used for the materials
I did a lot of intermediate renders to get a better idea of how the final version should look. I often draw sketches over these renders.
Drawing over intermediate renders to get a better idea
For the final rendering, the gamma was 1.8 (for a cartoon-style approach). Ambient Occlusion was used for emphasizing various parts. Light Cache for less noise and three different ZDepth with varying degrees. It helped to isolate the required sections for post-processing.
That way the artwork looked without Photoshop
If you look closely, the differences from the final version are not much; a slight haze, photo of the sky on the background (there are a few photos of canyons and clouds), and fire out of the barrel. This fire, the glow of the caterpillars and little things such as the drawn hands were created with brushes in Color Dodge mode and overlay. The secret of a cartoony look is a very strong filter Noise Reduction, applied several times.
The final image