Changing Native Mobile app background color/ adding background image

Hi all,   I would love to either change background color or changing background image in native mobile. I have seen that theres a “background image” in native page but when I added the image inside the widget, there is no effect.    How do I change either one of these? Are there any tutorials in the Mendix Academy or other websites? I tried finding for it but theres not much resources. 
1 answers

This post for instance covers some ways to do this (check out the accepted answer).