Use your profile to tell customers and shoppers a little about who you are and what you do.
A banner is a custom graphic shoppers will see when they visit your Supermarket store (at yourname.supermarkethq.com). A banner isn’t necessary, but it’s a good way to impress shoppers with your "brand" and/or your awesome Photoshop skills.
If you have a logo, be sure to upload it so it appears on your product pages and in your store. If you don’t have a logo, just upload a photo.
Note: if you don’t upload anything, there’s a not-very-cute placeholder image that will show up.