...
The site’s home page
Confluence pages and blog posts
Confluence space landing pages
Jira Software project landing pages
JSM project landing pages
Add a preview image and text to a page
Click the … Three dots button > Add Preview image & textmetadata.
...
Image guidelines
To optimize the preview images for the pages and news modules, follow these guidelines. While it is possible to upload an image in a different ratio, keep in mind that the module will crop it to fit the format.
...