How to use the shaders or node:
Append it from the file cellskins.blend (file/append/...goto file... /materials/...) choose the material you want.

Adjust the parameters of the shaders or node:

• reptile-colors: the top/edge/gap color of the cells (advanced users choose textures as input here)
  The humanskin just has one color channel (to input an imagetexture here)
  
  
• scale: the scale of the pattern (higher values make smaller cells)
  
  
• stretch: how much shall the surfaces curvature influence the pattern of cells
  The stretch factor changes the cellstructure depending on the pointiness of the surface.
  Pointiness then varies between scale*(100% + 0.5*stretch%) and scale*(100% - 0.5*stretch%) Therefore in areas where pointiness changes much, squeezing occurs.
  While in other areas where pointiness is constant it will look unstretched and has a certain scale.
  
  
• noise: how noisy the cells are
  
  
• bump: the bumpstrength of the cells
  
  
• contrast: how sudden curvature changes scale of the cells. This parameter is in reptile material and humanskin material.
  
  
• offset (for advanced use): Define the mean curvature of your model to the shader.
  A creature usually needs negative value between 0% and -50% (as it is a closed surface, hence a convex surface) a flat plane or landscape would use =0% offset, as its mainly flat. A concave model could use positive offset. But this really depends on the characteristics and also on the details of your model, and what you wnat to achieve. So just play with this setting, and look whats best for you. :)

If you use the shaders for animation, be sure to input a UVMap into the Vector Input of the shaders or the node. Otherwise the cellpattern may flow along the surface, as the model moves. Preceed as you would with fractal-textures.