Man oh man, I wish they had used that painting of the Jabberwock as the final design. It's an interesting and faithful update of the original Jabberwock illustration. The shapes and proportions of the final design are much more boring and generic. That griffon looks pretty sweet as well; I wish they'd included it.
I agree with you on the White Castle piece. Beautiful. Again, superior to the final design used in the film (though I did enjoy the designs of both castles, and their denizens.)