Another french site (yes.. they do like their japanese stuff.) with quite a extensive galleries from Kazuo Oga Art Collection artbook.
Kazuo Oga is a art director and primary Background Artist for many Studio Ghibli films. His quality of work is quite amazing.... The color palette of his paintings reflects perfectly the mood of the movies.
If anyone else have good reference of his artWork, please let me know. There is a remarkable lack of good japanese anime background painting.