Ok , it seems that once i put the app on the amazon app store, it might be possible to use the best icon. references: Http://mobile.tutsplus.com/tutorials/android/getting-started-with-kindle-fire-development/.
The icons on Kindle Fire are dynamically pulled from the Amazon Appstore for Android. Side-loaded apps cannot use this feature. Once you've submitted your app and it's live in the Amazon Appstore, your app's appropriate icon will automatically be displayed.