Background Image for mobile only

Is there a way to change the background image when on a mobile device i.e. when the browser is under “x” amount of pixels?

Currently, I have the background image sized through Custom CSS to:
body {background-size : 100% !important;}

It looks excellent on a desktop browser; however, it looks horrible in a mobile browser because a mobile browser is tall compared to a wide desktop browser. Am I able to set the background to change to a different picture when the browser is under a certain amount of pixels?

Thanks!