the title and image that Linked In will use is set using Open Graph meta tags. For example:
<meta property="og:title" content="your title here" />
<meta property="og:image" content="http://yourdomain/images/image.jpg" />
you could use the same recordset that you use to show the title on the page to add the title to the Open Graph meta tag.
you could add an image content area to your blog template, to set the linked in image, make sure to use a full url for the image, and use the developer notes to populate the image.