iOS:在导航条下面添加一个固定的图像

It feels like this should be fairly simple but nothing i've tried so far has worked. In a nutshell, I want to add a fixed image just below the navigation bar in a UITableViewController that i create programmatically. In other words, I want the image to stay just below the navigation bar even as the user scrolls up and down the table view (it's basically a custom drop-shadow for the navigation bar). It feels like this should be fairly simple but