You can define a theme and then set this for your PreferenceActivity in the manifest. Your theme can then define a a background color or a windowBackground image should you prefer that.
Manifest:
<activity android:label="@string/app_label" android:name=".client.PreferencesActivity"
android:theme="@style/PreferencesTheme">
<intent-filter>
</intent-filter>
</activity>
Then add the theme to your styles.xml
<style name="PreferencesTheme">
<item name="android:windowBackground">@drawable/background_image</item>
<item name="android:background">#FFEAEAEA</item>
</style>
In the above snippet there’s both a background color and a background image defined to show how to do it.