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:
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.