Not sure I understand what the purpose of this would be. A global container field is the same across all records. The only way you could get multiple photos into one would be to use a global container field with repeating values...and it would have limited usefulness.
What is the problem you are trying to solve?
What I try to work in the container field is I would like to drag and drop multiple photos into the container field object. each time no matter how many photos have been draging into the object; when dropping all into the object, all will be stored into the database.
I'm not sure, this would be clear enough or not.