We have a bunch of illustrations of the Spice and Wolf novel in http://danbooru.donmai.us/pool/show/83 for example. They're not tagged with the artist however, and we don't even seem to have a tag yet for this artist. According to wikipedia the illustrator is 文倉十 (Ayakura Jū), so would the tag be ayakura_juu?
Updated by 葉月