I don't think this can work. Remember that a container field is one field on one record so it always expects just one object. Multiple photos would need to end up in multiple records, you simply can't have multiple objects in one field.
A way to do this would be to have a global container field that has a trigger on it to create a new related record on a 'container' and set that to the contenst of the global field.
Of course you could not use that global field to view the photos
You need to write a script to import your images, you can point to a folder of images and FM will create a new record for each image. I have DB's with 10,000 plus images in which took seconds to import.