Here are the different user types and permissions members of an image bank can have:
Owner: The owner has all the rights as stated below and also have the rights to assign people the roles and permissions.
Administrator: As an administrator, you can reach the "Content Administration" page where you upload images, create collections, share collections, invite people, assign roles and permissions.
User: As a user, you only have access to the public page on the web. There you can download the images in the collections that are published.
Billing Rights: The owner of the image bank can choose who has billing rights. If you have the billing rights you have the rights to perform actions that cost money, such as inviting new users, launch image requests and purchase images from image requests.
Approval rights: Administrators with approval rights approves uploaded images and created collections that an admin without approval right has done. If you as an administrator without approval right have made collection or have been uploading images, these need to be approved before visible for all users.
In the add-in, all users have the same experience regardless of the roles or permissions. It's only on the web where it will affect which role you have been assigned.