Thumbnail does not show on link share.

Hello, when I share my domain link on forums, twitter, linkedIn, Facebook, etc........ my thumbnail is not grabbed. It will automatically pull my site-description. But, not my thumbnail image. Please help.

To see for yourself: GO to Facebook or LInkedIn and enter this as your status update: www.sopeachy.com Hit Enter but do not Post. You will notice that the website description is automatically generated. But....... where is the thumbnail????

With other domains, the thumbnail is always pulled in.

Thanks.