I found an article which might be interesting in terms of resurrecting this thread--a companion to
Esty's bad Tolkien art thread!
While I'm not convinced by all of the points made in this article, it is still an intriguing approach, to suggest that Tolkien's imagination was fired by art and illustration as well as by literary texts. Since Tolkien was a talented amateur artist, such an idea at least offers grounds for considering the breadth of his imagination. And why miss an opportunity for considering his relationship with Art Nouveau?
Perhaps we might also have a key here to understanding why some illustrators of Tolkien find approval among the Barrow Downers and others don't. Do illustrators who stray too far from Art Nouveau style risk breaking that intangible thread of imaginary visual sense? (Hey, I might post this idea on the bad art thread.)
Tolkien and the New Art: Visual Sources for Lord of the Rings