Payment of outstanding invoice and leaving AWS organisation to be a stand alone AWS account.

To pay an outstanding invoice when you cannot access the payer account in your AWS Organization, you should create a case in the AWS Support Center to get assistance with the payment issue and your specific organizational setup.

Regarding leaving the organization to become a standalone account: When an account leaves an AWS Organization, it becomes responsible for its own billing going forward. However, there are important considerations:

1. Payment responsibility: Once you leave the organization, you'll be directly responsible for all future charges. Your account will need to have a valid payment method set up, which you've indicated is already in place.

2. Outstanding invoices: Charges incurred while you were part of the organization typically remain the responsibility of the management (payer) account. However, if there are any charges from before you left the organization, these need to be resolved. This is why contacting AWS Support is crucial - they can help clarify the payment situation for your specific case.

3. Impact on existing data and services: Leaving an organization is primarily an administrative and billing change. Your existing AWS resources, including any S3 buckets or other services hosting your images, should remain intact and continue functioning. The images and data stored in your account will not be deleted simply by leaving the organization.

4. Access and retrieval: Your website's ability to host and retrieve images should not be affected, as the underlying AWS resources and their configurations remain with your account.

I strongly recommend contacting AWS Support through the Support Center before making any changes. They can help you resolve the outstanding invoice issue and provide specific guidance for your situation to ensure a smooth transition to a standalone account without disrupting your services or losing data.
Sources
Making payments - AWS Billing