Superman Homepage has what appears to be three international posters for Superman Returns that look quite good. Unfortunately the pics are a bit small, so hopefully we’ll be seeing higher resolution versions soon.
Check them out at the link above.
UPDATE: ‘Retroman’ has confirmed that these are indeed the real thing:
A small update the story of new posters that I think may interest you. As it turns they are the real deal and they are now on display at the Cannes film festival.
Source: Superman Homepage