Sponsored Brand ads are the only ad type that helps advertisers tell their brand story. It features a brand logo and a tagline. Now you can also add a custom image to showcase your brand or product in use. Custom images are displayed on desktop, tablet, mobile app and mobile browser at the top of customer search placements.
You will find the custom image option in the Creative section while you create a Sponsored Brand Ad campaign.
Amazon recommended custom image size: 1200 x 628 pixels, under 1 MB and in PNG, JPEG or GIF file format.