SketchUp has a very nice library of materials for models. If you need more materials, they are available at SketchUp Textures. Registration is free and you are welcome to support this effort as a club member for just $12/year. Club members receive several nice advantages, well worth $1/month!
There are times when materials repeat in an undesirable way when applied in SketchUp. IRender nXt includes a method that can solve tiling problems.
Here are two examples using fabric material samples.
First, and example of a fabric that does not tile properly. The Book Matched method resolves tiling for this material.
Second, an example that is solved using the Radiused method.