User votes control which image is displayed. Feel free to upvote the one you prefer.

It seems to have sorted itself out naturally via the voting process, however according to the contribution bible "Moderators can set a poster as primary when needed, for example when the top-voted poster is not title-only, has an imperfect aspect ratio or when a better poster is uploaded." This seems to be at odds with your response, as in this case I reported due to the top-voted poster at the time containing a ton of other text and a title-only poster being available.