Someone, on about the fifth page, added an image of The Dude, and now that's the topic's "image" when embedded into other discussions, topics, articles, etc. across the site.

I looked elsewhere and searched, but didn't see the answer: is there a way to easily (or even not-so-easily) change the image that's used to create these? Heck, I'd pay for a plugin to do it.

Waiting to be approved:

 

Thanks @Adriano Faria. This plugin does what I want and gives me (and my moderators) control over the image. I no longer have to stare at The Dude's boxer shorts and robe.