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You need to utilize a mass upload feature. currently the plugin does not support images because it would be too time consuming and defeat the purpose of the plugin as a csv ingestor. http://codex.ww.wp.xz.cn/Post_Types

attachment is a post type which points to a file in wp-content/uploads. You could theoretically upload all images to that folder and create a csv of all the attachment posts you want to ingest with their respective post parent associations. the only issue is that you would still have to delete the existing associations which is outside the scope of this plugin.