Suave uses Advanced Custom Fields to add some additional fields to WooCommerce Product Categories. These are setup when you import the theme demo data. If you didn't import the theme demo data you can still easily setup these additional fields by importing the XML file below.
To import this file, go to
Tools -> Import -> WordPress. (Install the Importer plugin if prompted)
Select productcatbanner.xml (attached)
Complete the import process. Once it's completed, you should see an additional field when editing your product category to add a category banner.
Go to 'Custom Fields' and delete all of the fields. You will also need to empty the trash/bin. Deleting them fully is very important. Then, try the import again.