Imagery which doesn't just fall into one category

Though classed as Illustrations, there is something I noticed about the majority of Harry Potter and the Deathly Hallow Part2 posters. I couldn't figure out whether they were photography or design like photorealism. Maybe its a mix of both?
CGI maybe?

This would be very good for something which was once a book. Without the illustrations and imagination and writing of harry potter, the films would not exist.
It keeps a bit of the orginal book and imagination.

Comic books made into films should keep a part of its original format at least on the poster or DVD cover, rather than changing it entirely.
So for example, with the marvel films it would be cool if they could look slightly comic arty and less 'lets pose for the camera' like a lot of the film posters are.