DETAIL BUMP MAPS

You can give your materials a certain texture to them, for example, make them appear like concrete or wood. You do this by applying a bump map in the Detail box - see below: 

1. Assign a surface type, eg concrete to get rid of the ASSIGN SURFACE TYPE! warning.

2. Assign a Detail bump map from the folder: textures/detail_bumpmaps. eg metal_ddn.dds:

metal_ddn.dds

3. Under Shader Generation Params tick Detail bump mapping

4. Under Shader Params play around with the following settings:

Detail bump scale: (how bumpy the surface will be)

Detail tiling U and V: (the scale the texture will be mapped. A setting of 100 will make the texture tile smaller than a setting of 1. I usually go for around 10, however if you've used the Sketchup default white material, you may need to use around .05

bump example 01

bump example 02

For further information on materials and textures, watch  CryEngine 3 : an introduction and application. Vol. 3 "Materials and Creating A Prop" and "Materials And Textures" found here.