The css3 animations reset to the default style at the end of the animation. You can try something with javascript:
You can add an eventListener to your animation, retrieve the styles you wish to keep, apply them manually and remove the animation.
document.getElementById('yourdiv').addEventListener(
'webkitAnimationEnd',
function(){
document.getElementById('yourdiv').style.backgroundPosition = '0px 0px';
document.getElementById('yourdiv').style.webkitAnimationName = 'none';
},
false
);