When I post my CRG url on a facebook message, it is converted to top blank image followed by the Title ( form Gallery fields ) and a description ( an excerpt from the Gallery Block), followed by my domain name.
What needs to be done to have some image displayed on the post / message ?
Should ensure a thumbnail is set in your publisher settings. If you're not using publisher, then you should be.
In fact, if you're using CE4, then you should consider moving up to Backlight.