[krasovsky]

<div id="page_cont">123</div>
<ul id="my_menu">
<li><a href="#" data-pic="somepic-1.jpg"><span>&nbsp;&nbsp;&nbsp;&nbsp;О НАС</span></a></li>
<li><a href="#" data-pic="somepic-2.jpg"><span>&nbsp;&nbsp;УСЛУГИ</span></a></li>
</ul>

$('#my_menu a').hover(function(){
  var pic = $(this).data('pic');
  $('#page_cont').css('background','url('+pic+') no repeat 0 0');
    console.log($('#page_cont'))
},
function(){
 $('#page_cont').css('background','ur(original-pic.jpg) no repeat 0 0');
    console.log(2)
}
)