Hello Simes,
You are partially correct with regard to the use and choice of the logotype but it's normally only the case with the big studio 'tentpole' releases. With something like Iron Man 2 or Harry Potter which rely upon additional merchandising deals (from fast food chains to toys), the use of a standardized logotype is somewhat more important in maintaining a consistent branding across all promotional platforms that can be instantly linked back to the film it seeks to promote.
The use of the image is more flexible depending on which territory we are dealing with. Sometimes certain actors/characters (when referring to a multi cast line-up like Oceans 11) are more popular in one part of the world than in others so their prominence on a poster is dictated by what the market research comes up with.
As for something like Black Swan, there is substantially more freedom to create an advertising campaign more intune to individual territories because it's not as restricted by the aforementioned merchandising deals.
There is obviously a lot more to it than this simplified description but the bottom line is that the entire campaign for Black Swan is one of the better and more interesting used this year and I'm definitely looking forward to seeing it.
Paul.