Android: how to create a background from pattern?

Here is a really nice explanation:

Put your "back.png" image on "drawable" folder. Then create a drawable "backrepeat.xml" like that:

<?xml version="1.0" encoding="utf-8"?>
<bitmap xmlns:android="http://schemas.android.com/apk/res/android"
    android:src="@drawable/back" 
    android:tileMode="repeat" /> 

In your layout, add android:background="@drawable/backrepeat":

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:id="@+id/MainLayout"
    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">

</LinearLayout>

As is the case with many Android good practices/handy tricks, it can be traced back to Romain Guy.