If Facebook does not generate a preview image when sharing a Leadpage URL, it is usually the result of Facebook not having indexed your images yet.
There is a simple solution to this problem.
Step 1: Go to the Facebook Developers’ site “Debug Tool:”
Step 2: Copy and paste the URL of the page you want to share on Facebook into the box and click “Debug.”
This forces Facebook to “crawl” the link to see if there is an image. If you scroll down into the debug results, you should now see an image thumbnail.
PLEASE NOTE: If there is still no thumbnail, Facebook may not be able to find an image for that page. You can manually “tell” Facebook what to use as an image by adding the information to your page, following the instructions here: How Can I Change The Preview Of My Page On Social Networks?
Step 3: Refresh your browser and try re-posting the Leadpages URL.
Facebook should now generate a preview which an image to post along with your link.
Please let us know if you have additional questions.
You can always file a support ticket if you have additional questions by clicking the Support button in your dashboard shown here or clicking here to file a support ticket.