Under copyright, as I understand it, the use of images (and other media) can occur without permission in the case of criticism and review. However, sites such as TierMaker uses images to represent what you are reviewing. To what extent is this allowed? For example, would this tier list of Harry Potter movies fall under fair dealing when they aren't reviewing the movie covers, but the movies themselves?
To confirm, I pose this in the context of UK copyright law, and specifically in the case of the use of imagery to represent material. (e.g one could argue that the imagery is superfluous in the reference of the critiques material, making it not fair dealing)