Shading & Textures
Here I will simply show you some of the settings.
I used a mixture of 2 materials. The base material is responsible for the diffuse shading and for the SSS. I didn't use the FastSSS because it doesn't let light in through an object from behind. Translucency is better for such effects. The other material (Coat 1) makes the reflections. It's totally black (except for the reflections, of course) and contributes in additive (shellac) mode, which means that it doesn't have any influence on the diffuse colour (Fig.08).
The textures which I used for the snail were scaled down to 512 or 256, but originally they were 2048 each. UVW was used for better orientation (Fig.09).
Because of the light and shader settings, the colour of the diffuse map usually differs to how it turns out in the render (Fig.10). The Bump and Normal maps were more or less generated out of this with a Photoshop plug-in. You can imagine this in blue, as the Normal map. Note: there's less bump on the eye area (Fig.11).
The opacity, in this case, controls the amount of SSS. Note: there's only SSS on the tentacles, under the eyes (with veins) and on the mouth (Fig.12). SSS controls just the colour, not the amount. I made a different colour for the mouth and left the tentacles white.
As you can see in the shader screenshot (Fig08), the Fog colour is green. This means that the SSS will be a mixture of the green and of this texture (Fig.13). (Specular/Reflection can be seen in Fig.14.)
The background and the bricks were made from photographs; the helix lines were painted (Fig.15).
The purpose of the thick black lines is that the gaps between the metal parts don't look too bright. The rust and scratches were pasted from photographs in subtractive mode (Fig.16).
I used a map from cgtextures.com; I edited it a little (colour and sharpness correction for the diffuse part, and some playing around with Gaussian Blur and contrast for the displacement and normal). (Fig.17 shows 100% zoom.)
I used two lights. The first was a VraySun from behind the car, to simulate the sun. This light was also responsible for the colour of the sky and GI (VraySky). For those who don't use Vray, what I used is a system that adjusts the colour of the sun dependent upon its angle (if it's high, it will be white daylight with blue shadows; if it's low, it will be orange with darker blue shadows). Also, the sky colour changes dependent upon the placement of the sun, so you'll get a blue sky for a high sun and an orange sky, as shown here, for a low sun (same as with GI). The second light was a Vraylight, which didn't affect the diffuse; it was blue and came from the left behind the camera. The goal was to make the reflections on the materials much more interesting. A screenshot of the lighting setup can be seen in Fig.18.