Ionic background doesn't display in app

According to the Ionic forum (http://forum.ionicframework.com/t/background-image/1731) the backgroun image should display if you put it on the ion-content from the css file, like I'm doing:

.scroll-content {
background:url(/img/splash2.jpg);
background-size: cover;
background-repeat: no-repeat;
}

but it displays in every page in ionic serve but in none if you run the app on a device.

Any ideas?