In the Android preferences you can put different types of controls: check box, edit box, list,…, but none of these displays an icon (see Settings).
Usually a preference consists of two lines, the title and the summary, and after you have clicked you get a dialog box where you can select the chosen item, as you can see in the two pictures below.
Just another tool to create Android icons, such as gimp-android-xdpi.
You can find at Script for creating Android Icons or at GIMP script for creating Android icons at once.
I found this very useful plugin for gimp, called gimp-android-xdpi, that allows you to easily create images with the desired dimensions in the directories drawable-ldpi, drawable-mdpi, drawable-hdpi and drawable-xhdpi of an Android project, following the guidelines explained on Icon Design Guidelines and links therein.