Sadly, from what I hear, one of the best things to come out of 'The Hobbit' was actually the trailer for 'Pacific Rim'. (Edit: Saw 'The Hobbit'... and LOVED it.) On the upside... Who doesn't love giant robots fighting giant monsters?
Very little artwork for the movie has yet been made public. But I'm sure when they make an 'Art of' book, it will be killer reference for SF buffs. In the mean time, here is a very small sampling of the only real concept/promotional art to be released thus far.