Heritage Auctions has an original concept sketch in their September 30th auction, by artist Toby Bluth. It is titled "Night Rider suggestion for 'Lord of the Rings'". ... ?itemid-121839_75007!wlem

The full description is as follows:
Toby Bluth The Lord of the Rings Night Rider Concept Drawing (Fantasy Films, 1978). Ink on paper by Bluth, featuring an approximately 7" x 8.5" concept design of a Ringwraith for Ralph Bakshi's animated adaptation of the novel. There's some scuffing, indentations, and a hole near the left edge. Overall in Good condition.