Icons allow for more meaningful associations. While text items have the potential to look very similar, different images can let the user connect the idea of the image with the idea of the part of the app it navigates to. Using icons with the same meaning as in other apps can further help the user connect them to functionality, for instance, using an icon similar to the App Store's "Updates" icon immediately tells the user that that screen will involve some sort of download/update functionality.
This is similar to the design for Apple's Home screen. When you launch an app from the home screen, most likely you don't look for the app's title text. You recognize the icon, and click on it probably before you ever read the text beneath it.
If you are going to use images, they don't need to be complex or distracting. Simple, flat and colorful images make for the cleanest experience.
Example: the final product from AppCoda's implementation of the slide-out menu - image