You can set the background image to an activity by setting android:background xml attributes as followings: (Here, for example, Take a LinearLayout for an activity and setting a background image for the layout(i.e. indirectly to an activity)).
Mobdro is 100% legal in USA. You donât need to worry about it. Up to now, there is no legal issues regarding Mobdro application. Mobdro streaming application is quite familiar to UK and US people.
At present in the US, there is no federal law against the sale of violent video games to children. However there is a system of self-regulation governed by the Entertainment Software Rating Board (ESRB).