ShareKit brings back the ability to edit link previews on Facebook - simply upload an image and enter a title and description, and ShareKit will generate a new link that can then be posted to Facebook with a beautiful preview
Piar.io - Create beautiful custom link previews for all your social media channels in one place
Design Principles - An open source repository of design principles and methods
Mugshot Bot - Automated link preview images for your website. No more fussing with design tools or wading through thousands of stock photos.
Atlassian Design - Design, develop, and deliver
Linkz.ai - Automatic rich link previews on hover that keep visitors on your website
Facebook Design Resources - A collection of free resources made by designers at Facebook