I've made my background image responsive in my :after psuedo but not able to control the height responsiveness so I end up with a big white space at the bottom of my image.
My CSS:
.element:after {
    content:'';
    background:url('http://i57.tinypic.com/4kdytv.png') no-repeat;
    background-size:100%;
    height:284px;
    display:block;
}
Fiddle: http://jsfiddle.net/w6amht6o/
I've seen a couple other questions like this but none of them discuss making the height responsive. I seen you could try something like "background-width:100% 100%;" but this did not work for me.
Let me know what I am doing wrong!