how to change Android overflow menu icon

You can try something like this:

<style name="MyTheme" parent="android:style/Theme.Holo.Light">
     <item name="android:actionOverflowButtonStyle">@style/MyActionButtonOverflow</item>
</style>

<style name="MyActionButtonOverflow" parent="android:style/Widget.Holo.ActionButton.Overflow">
    <item name="android:src">@drawable/my_action_bTutton_overflow</item>
</style>

and in AndroidManifest.xml

<application
    android:theme="@style/MyTheme" >

If you are using AppCompat you can achieve by following code.

res/values/themes.xml

<style name="MyTheme" parent="@style/Theme.AppCompat.Light">
     <item name="android:actionOverflowButtonStyle">@style/ActionButtonOverflow</item>

      <!-- Support library compatibility -->
     <item name="actionOverflowButtonStyle">@style/ActionButtonOverflow</item>

</style>

      <style name="ActionButtonOverflow" parent="@style/Widget.AppCompat.ActionButton.Overflow">
            <item name="android:src">@drawable/ic_launcher</item>
        </style>

and in androidmanifest.xml

<application
    android:theme="@style/MyTheme" >

Define a custom style: for example, let's call it customoverflow.

In this style you set android:src to the picture you would like to use. Now create a style with parent Theme.holo.

In this style you need to define:

<item name="android:actionOverflowButtonStyle">@style/customoverflow</item>

I just tested this and it works.