File:Wiki.png

Summary
The algorithm seems to default to Wiki.png when it can't find an image in the page to use as its image in the html meta tags. So setting Wiki.png to the image that is wanted as the default image should fix that. The previous Wiki.png will be located at File:WikiLogo.png and the Mediawiki:Hydra.css and Mediawiki:Hydradark.css style sheets will be updated to show the WikiLogo.png image in the top left.