WordPress Pictures Will Not Show When URL is Used on LinkedIn

Hey i’m having problems with my customised word press theme.

Every time I link to a blog post in LinkedIn or Facebook none of the images used within the wordpress post are shown as a small ‘preview image’ they use on these sites.

I’ve set a ‘feature image’ in every post on wordpress yet this doesn’t seem to have any affect.

If there’s any advice out there that would be great. I’ve looked everywhere and can’t find a solutions.

The blog can be found here:
http://www.branchingouteurope.com/blog