To use Holo theme on Andriod, simply add the following in your tiapp.xml file. You are using a device that does not support this theme, it will fallack to the default theme on 2.x automatically.

tiapp.xml

<android xmlns:android="http://schemas.android.com/apk/res/android">
    <tool-api-level>16</tool-api-level>
    <manifest android:installLocation="preferExternal"
        android:versionCode="3" android:versionName="1.0.2">
        <uses-sdk android:minSdkVersion="7" android:targetSdkVersion="16"/>
        <application android:theme="@android:style/Theme.Holo">
            <activity
                android:configChanges="keyboardHidden|orientation"
                android:name="org.appcelerator.titanium.TiActivity"
                android:screenOrientation="portrait" 
        android:theme="@android:style/Theme.Holo"/>
        </application>
    </manifest>
</android>