Facebook og:image 在用户分享话题时未被抓取

Not sure if this merits creating a separate topic, but has there ever been a thought of setting up a field for og:image that could be used for categories and the community as a whole? I typically want to invite people on Facebook and promote for users to participate in a specific category, but the graphical call-to-action is certainly lacking. And I’m not sure if anyone has found a good way to get around this.