A thumbnail image of Rickman as Snape would indeed be fair use, as described in the policy.
If that's the case, than I'm still not convinced all the complicated copyright information is needed as the only place where you could add a picture of Rickman as Snape would be the Snape character page or the Rickman actor page. Adding a copyrighted image therefore would be covered by "If you don't own it, don't add anything bigger than 150 KB" and "Always add a source!" All you would have to do is include a general note to the image policy page that we consider using these kind of images for illustrative purposes fair use.
Re: is anyone looking at usability and inclusiveness?
If that's the case, than I'm still not convinced all the complicated copyright information is needed as the only place where you could add a picture of Rickman as Snape would be the Snape character page or the Rickman actor page. Adding a copyrighted image therefore would be covered by "If you don't own it, don't add anything bigger than 150 KB" and "Always add a source!" All you would have to do is include a general note to the image policy page that we consider using these kind of images for illustrative purposes fair use.