I have done things like this using a Global container field and a script. In my case it was one container field per record, but you may be able to script field selection by looking for the next empty field in a sequence. If they are all full, create a new record and start with the first field.
I had the script trigger using an OnObjectModify script trigger on the global field. If an image was there, the script created a new record and put the image in the container field. The it cleared the global container to set up for the next image.
You did miss that MBS Plugin has a Drop area feature to receive drops of pictures?