Change displayed primary poster on main credits page

As you are probably aware of, many main credit pages do not display an aprropiate film poster. Instead, there are photos of movie stills, bad box artwork, atrociously bad photoshopped covers and in some cases film posters of bad quality. After looking into the gallery, however, more often than not you find that there is a perfectly suitable film poster already beeing uploaded.
My idea now is, that after enlarging a picture in a gallery the users should be able to "flag" it via a "Primary Poster" button in order to give you the information to change the poster displayed on the main credit page - or even for the user to make the changes instantly.
Also a button for "Wrong Poster" would be a great idea since I have stumbled across a couple of posters which are in a wrong gallery altogether.