Over on the official Japanese Sonic Unleashed site, new character art for Chip and Robotnik have been released. Chip is a new character from the Sonic Unleashed manga (eH?) who likes ice cream, and will be added to the list of Sonic character rejects that grows with every game. Apparently the character art has disappeared off the site, so you can see it here.
The Japanese site also has a background featuring all the levels featuring in the game. Two previously unseen ones are present; a snow level (Holoska) and a New York level (Empire City). This level seems to be based heavily on New York, with real-life skyscrapers visible such as the Chrysler Building. The loading bar has a nice '90s demoscene-style rotating globe as well. Lovely.