I have an image on a webpage, but the souce URL for that image has an ID at the end, and this ID changes every time the page is reloaded. This is so the image does not remain cached, and the latest version is loaded every time. However, would Google or any other search engine see this as dubplicate content?
No, that is not duplicate content. This is a normal and common technique to ensure that a resource is fresh and not cached. This will not cause you any issues as this is not what Google is trying to eliminate from their search results.
It shouldn't be an issue, but if you're worried about it you can tell Google to ignore these types of things if you have a Google Webmaster Tools account. Log in to webmaster tools, choose your site on the right, and then under the site specific options under crawl, you should see a "URL Parameters" option. There you can add the image id parameter and explicitly tell Google to ignore it.