By default, the link share image that is pulled by Twitter, Facebook, and other social networks will be the cover photo of your story.
Under your Story Options, you have the ability to set a custom link share image that will replace using the cover photo for a link shared.
The optimal image size is 1200px ร 630px, but any image under 5MB will be cropped to that size once uploaded and processed.
This feature is available on any paid plan.
You can confirm what your link will look like via these handy links.