Implement a manual review process where each VM deployment is checked by an administrator to verify the image source before approval.

Create a custom Azure Policy definition that specifies the approved VM images and assign this policy to the relevant scope (subscription or resource group).

Rely on the default settings in Azure without creating any custom policies, assuming that all deployments will comply with organizational standards.

Send an email to all IT staff reminding them to use only approved images for VM deployments, without implementing any automated checks.

Use Azure Blueprints to package the custom Azure Policy along with other artifacts to ensure consistent deployment and compliance across multiple subscriptions.