Here are some pretty cool designs of the dragon Smaug that were not used in The Hobbit: The Desolation of Smaug. These came directly from artist Andrew Baker, who works for WETA. These are designs that he came up with that will be included in the book The Hobbit: The Desolation of Smaug: Smaug: Unleashing The Dragon.
I love seeing the concept art used for a film. It is interesting to see the thought that is put into developing these kinds of movies.