$(document).ready(function(){
    $("#searchSub").click(function() {
      $(this).toggleClass("activeDrop");
      }
   )
});


css here


#searchSub {
   height:30px;
   width:25px;
   background-image:url(files/search_new.png);
   background-position:26px 0px;
   margin-left:-4px;
   float:right;
}

.activeDrop {
   background-position:26px 93px;
}