[Aetae]

(function() {
  var imgArr = ['url(./img/pic_0.png)','url(./img/pic_1.png)','url(./img/pic_2.png)','url(./img/pic_3.png)','url(./img/pic_4.png)'];
  var background = ['url(./img/podlojka.png)','url(./img/podlojka_empty.png)']
  var red = ['#430606','#cd5d5d'];
  var yellow = ['#ffc601','#ff8d06'];
  var wallpaper=document.getElementById('wallpaper').style;
  function toggle(e) {
    var i=this.id.slice(-1);
    var type=+((e||window.event).type=='mouseover');
    this.style.backgroundImage = background[type];
    document.getElementById('under_price'+i).style.color = red[type];
    document.getElementById('old_price'+i).style.color = yellow[type];
    wallpaper.backgroundImage = imgArr[i-type];
  }
  for (var i=0;4>i++;) {
    var element = document.getElementById('price'+i);
    element.onmouseover = element.onmouseout = toggle;
  }
})()

Как-то так. Но на самом деле это делается через css классы.