Since the slider operates dynamically (pulling the most recent thread/articles/blogs, etc), there really isn't a good way to try to accomplish this. With that said, here are a couple ideas...
To do it right now, create a custom content type for the particular article you are talking about, using the desired image, and linking back to that article.
As a possible future option I've been contemplating, creating a custom IMG BBCode which could be used for the desired image, and then have a setting to search for that specific BBCode, and if not found, default to either the ATTACH or IMG tags instead.
Brad via Tapatalk