Added am icon for the theme preference

app/src/main/res/drawable/ic_palette.xml

+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:autoMirrored="true"
+        android:height="24dp"
+        android:viewportHeight="512"
+        android:viewportWidth="512"
+        android:width="24dp">
+    <path
+            android:fillColor="?android:attr/textColor"
+            android:pathData="M204.3,5C104.9,24.4 24.8,104.3 5.2,203.4c-37,187 131.7,326.4 258.8,306.7 41.2,-6.4 61.4,-54.6 42.5,-91.7 -23.1,-45.4 9.9,-98.4 60.9,-98.4h79.7c35.8,0 64.8,-29.6 64.9,-65.3C511.5,97.1 368.1,-26.9 204.3,5zM96,320c-17.7,0 -32,-14.3 -32,-32s14.3,-32 32,-32 32,14.3 32,32 -14.3,32 -32,32zM128,192c-17.7,0 -32,-14.3 -32,-32s14.3,-32 32,-32 32,14.3 32,32 -14.3,32 -32,32zM256,128c-17.7,0 -32,-14.3 -32,-32s14.3,-32 32,-32 32,14.3 32,32 -14.3,32 -32,32zM384,192c-17.7,0 -32,-14.3 -32,-32s14.3,-32 32,-32 32,14.3 32,32 -14.3,32 -32,32z"/>
+</vector>

app/src/main/res/xml/preferences.xml

@@ -4,6 +4,7 @@
     <ListPreference
             android:defaultValue="1"
             android:entries="@array/theme"
+            android:icon="@drawable/ic_palette"
             android:entryValues="@array/themeValues"
             android:key="theme"
             android:summary="@string/summary_theme"