This plugin aims at providing users the capability to upload multiple thumbnails/featured images to a post. It uses wp.media js object to open a image uploader frame and choose/upload images. Once the images are selected, it will save the id of uploaded media object in a custom field.
You can use the function aoc_get_images($post_id) to retrieve an array of urls of all the images that have been uploaded to a post. This function accepts the id of post (for which the images are to be fetched) as a parameter.