That's because FB does not see opengraph meta tags on your site with a specific image and thus retrieves the first one it can scrape from the HTML output of the site. SocialConnect does add opengraph tags but on content entities like articles, items or products. For the frontpage, check if your template supports adding opengraph meta tags (like our templates) or simply add them on your own. To do that, check the HTML output of www.joomlaworks.net and copy the meta tags that start with "
For further assistance, don't hesitate to post in our support helpdesk.

As a sidenote, we could add some fields in SocialConnect settings, so even if your template does not support adding opengraph meta tags for the frontpage, you can use SocialConnect to do so.