That's the OG (Open Graph) Image. It's an image built into the site that's used as the thumbnail for shares on social media and messaging apps. (More info on OG Images here: https://layerre.com/glossary/open-graph-image/)

How could I change the image to be less intrusive? I can't have it show an image of the message you're trying to share, because the server never sees that message. But can I make the default image nicer on the eyes.