There was a recent update to the blogging platform the I use to create posts. When you place an image topper for a blog posts, that same image will become the header for the full entry page of that particular blog posts. This adds to a more professional look and feel to your blog posts and allows the user to experience a more concentrated view of the subject matter based on that particular image. Also, it adds a bit more interactivity to that posts that was not there before.
I look forward to the continued improvements to the Alloy blogging platform. I know that there are some cool updates coming in the very near future.