There are plenty of rumors going around about the iPhone 5S, including things like a dual-LED flash and a fingerprint scanner. Now, leaked components of the next-gen iPhone show changes to the top of the back and around the home button, which might be due to the inclusion of just those components. Another noticeable change in the components is that the mounting points for the motherboard...
Source: http://www.gsmarena.com/photos_of_iphone_5s_chassis_components_surface-news-6573.php