Tabs gradient or image background

How to override the $tabs-dark-background in the ionic.app.css file with a gradient background or image background,

this works:

$tabs-dark-bg: #333 !default;

but this isnt working:

$tabs-dark-bg: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#222), color-stop(100%,#333)) !default; /* Chrome,Safari4+ /
$tabs-dark-bg: -webkit-linear-gradient(top, #222 0%,#333 100%) !default; /
Chrome10+,Safari5.1+ /
$tabs-dark-bg: linear-gradient(to bottom, #4c4c4c 0%,#131313 100%) !default; /
W3C */

Any ideas, this is driving me crazy, such simple thing in sass couldn’t be done, i could do it modifying the mixing it is suppossed we should do it that way, because if we update ionic, this will be override.

@mixin tab-style($bg-color, $border-color, $color) {
border-color: $border-color;
background: rgba(73,155,234,1);
background: -moz-linear-gradient(top, rgba(73,155,234,1) 0%, rgba(32,124,229,1) 100%);
background: -webkit-gradient(left top, left bottom, color-stop(0%, rgba(73,155,234,1)), color-stop(100%, rgba(32,124,229,1)));
background: -webkit-linear-gradient(top, rgba(73,155,234,1) 0%, rgba(32,124,229,1) 100%);
background: -o-linear-gradient(top, rgba(73,155,234,1) 0%, rgba(32,124,229,1) 100%);
background: -ms-linear-gradient(top, rgba(73,155,234,1) 0%, rgba(32,124,229,1) 100%);
background: linear-gradient(to bottom, rgba(73,155,234,1) 0%, rgba(32,124,229,1) 100%);
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr=’#499bea’, endColorstr=’#207ce5’, GradientType=0 );

color: $color;
}

also would like add border to each tab, thanks in advance!