i have not tried this thing but i think in 4.7 we can do this.
1. using google map api get the my location in (lat and long).
2. using google map api get static map of my location and save in flash memory or a microSD Card.
Code:
String uri = file:///store/home/user/pictures/my_location.jpg
3. set the background image on home screen using.
Code:
net.rim.blackberry.api.homescreen.HomeScreen.setBackgroundImage(String uri)