Does anyone know any good websites concerning this subject??

Do you mean Yoshitaka Amano's Artwork? I don't know... I merely have the Artbook.
I could scan it if had a scanner... sorry ~.~

But the artwork is truly pretty ^^

Here are a few links you can try..

www.amanosworld.com
http://coco.raceme.org/videogames/amano/ff7.php
http://www.fantasysquare.com/fanart/amanotribute.asp

Too bad you don't got a scanner. I really would've wanted too see the the artbook,Katayoku no Tenshi. Where did you buy it anyway?