Are the images added in an image collection (via StudioPro) or were they added as objects in de application?
Files uploaded in the app will be stored in a folder structure and the reference is stored in the database (file entity). If you for example backup and restore a database, without the actual files, you will indeed still have a reference in your app, but the actual file is missing.
So in your cloud environment, you may need to upload the files (again).