Add Image_src Meta Tag Wordpress Plugin - Rating, Reviews, Demo & Download
Plugin Description
This plugin helps ensure your content has a relevant thumbnail when shared on social sites. If your articles have no image associated with them when shared on social sites, or worse, if your RSS icon keeps showing up as the thumbnail this plugin will help you define the correct image to be used.
Adds an image_src meta tag to your header using post thumbnnail. You must have post thumbnails / featured image enabled in your theme for this plugin to be effective.