Good explanation Csaba.
Here is more info on textures subject:
http://www.google.com/intl/en/sketchup/3dwh/acceptance_criteria.html
"Models should be completely photo-textured.
Use photos of the actual structure to "paint" your model.
More detail
We recommend using high-quality and properly sized photographs to produce textures:
* Texture the entire model, including the roof. For faces that can't be photographed, such as the roof, use the imagery in Google Earth. If Google Earth's imagery is too blurry, or, outdated (the building was developed after the imagery was taken) then it's acceptable to use SketchUp materials provided the color and scale are as accurate as possible.
* Use one photo for a face to enhance a model's realism. Please make sure that the face is completely covered with the photo, and no sky or ground imagery can be seen.
* We suggest using images that are greater than 256 pixels wide but less than 512 pixels. It's possible to use images greater than 1024 pixels and less than 2048 pixels; however, files larger than 10MB won't be accepted into the Google 3D Warehouse."