Visit the developer’s toolbar and click the "Edit" link.
Scroll down (under the screenshots section) and upload images for your extension:
Images will be placed in the viewing queue after it is uploaded. If the images meet the criteria for promotional images , it will be displayed in the web store for several days.
You will not receive any notifications when images are received (dis). Send a message to cws-assets@google.com to request the status of your images. And no, you cannot see the status on the dashboard, contrary to what the official documentation says