Android : How to add bitmap on preference?

how can I add my imported images on my preference? I want to have a settings that the player can choose what his desired character?

this is the screenshot of xml:

<ListPreference
            android:key="bitmap"
            android:title="Character"
            android:entries="@array/bitmap"
            android:entryValues="@array/bitmap_resources"
            android:dialogTitle="Select Character" />

in my array

<string-array name="bitmap">
    <item>Car</item>
    <item>Ghost</item>
    <item>Human</item>
</string-array>
<string-array name="bitmap_resources">
    <item>**???**</item>
    <item>**???**</item>
    <item>**???**</item>
</string-array>

in my class

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
Drawable bitmap_char = getResources().getDrawable(R.drawable.hero);
    String bitmapStr = prefs.getString("bitmap", "");
    if(bitmapStr.length() > 0) {
    }

where am I doing wrong? I can vote for any help or suggestions. thanks.