9-Patch will stretch, You have to specify which area should stretch in the image. Why dont you try repeating your drawable. like so:
<xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:id="@+id/YourLayout"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:background="@drawable/backrepeat"
>
then in an xml called backrepeat.xml
<bitmap xmlns:android="http://schemas.android.com/apk/res/android"
android:src="@drawable/back"
android:tileMode="repeat" />