BackgroundImage can't override NavigationBar

Hello guys, I'm using a MasterDetailPage and i have a backgroundImage in the Detail page (the one showed at first).
I would really like that the image can "overrides" the navigation bar, so that i can have a full screen with the image and in the top left the hamburger menu icon. Instead i have a blue navigation bar and down the image covering the rest of the screen. I can't manage to extend the image in order to cover the navigation bar too, how can I achieve this?
Many thanks