Art of Blender
The Art of Blender is full of inspiring renderings from Blender artists around the world.
In this Blender 2.5 video tutorial we do some fairly intensive sculpting on creating a rock face. This tutorial makes use of a technique very similar to sketching by layering large numbers of stroke over one another to automatically create much of the detail.
All references are licensed under Creative Commons and can be here at the below links or in the included references folder: