The latest TV spot for The Hobbit: An Unexpected Journey features a few scant shots of Smaug. And I mean very scant. He just swoops in and destroys stuff, sort of like what he did in the Star Trek Into Darkness poster this morning (aka The Star Trek Rises).
Peter Jackson has stated that Smaug only makes a cameo in this first Hobbit film, so we'll have to wait until The Hobbit: The Desolation of Smaug to see the dragon in full and hear Benedict Cumberbatch's voice. As for Smaug's design, Jackson said the following to the LA Times/Hero Complex:
The Hobbit: An Unexpected Journey arrives in theaters December 14th. And remember, you can still get your Tolkien-themed diabetes at Denny's.