Sorry, not possible at this time. This is on my todo list. How it’ll work when I add the feature… You would add a column for the image name and upload the images to a specific folder on the server via FTP. When Connections displays an entry, it’ll first look in that folder for the image name and if found, it’ll move it to the entry’s image folder , create and cache the required derivative for all future use. All the work has been completed in the Connections core plugin. The CSV Import needs to be updated to use this new new feature.
Sorry, this does not help you now.