Android : How can i set an image to be in the bottom left corner of an activity AND in the background

I want to set the logo of my app to the bottom left hand side of the screen and be in the background. the reason i want to do this is to allow the users to modify the background colors which would not be possible if i simply set the entire activity or layout background to an image to give same impression.

Another way of asking this is how do i set an image to bottom left hand corner and below other controls?