CoSchedule currently supports Link Preview customization for Pinterest only. This option is limited due to many networks removing this capability.
Using A Custom Image on a Pinterest Message
Custom images can be used on any links you're scheduling to Pinterest by first creating a new social message (either directly on your calendar, or in a Social Campaign) followed by selecting a Pinterest board. Click "Link" as the message type, and enter a link into the Permalink field:
Clicking on the "X" will allow you to remove the image that's automatically pulled from this link. You can upload a custom image by clicking in the box after.
After replacing your image, you'll see it used as the image tied to your link when Published on Pinterest.