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Check them out. James himself posted the link in his blog: it contains low res versions of a fables cover and the main illustration for one of his process recess books, as well as a word document with some info about how he makes his images.
Enjoy! I found them useful.
Any luck finding those files?
I think James Jean is a genius. By far one of the best illustrators alive. The reason, most likely, that he doesn't want to share those files is because his art has changed and improved greatly since 2008, and continues to do so.