While the plugin listing that we put in place by creating a readme.txt
file and uploading it to the official plugin repository is perfectly functional, it does not really stand out among the sea of extensions that are available on the website. Thankfully, https://wordpress.org introduced a mechanism allowing plugin developers to add a banner image to their listing. This image can be anything from a simple picture to a complex graphic to advertise your creation.
This recipe explains how to prepare images for your plugin and how to upload them to your repository.
You should have already followed the Applying for your plugin to be hosted on wordpress.org and Uploading your plugin using Subversion recipes to have an approved repository on the official repository and plugin files uploaded to the server.