How to change each button of pickList

[padmajakrish]

.ui-picklist-button-add{
background-image: url(images/addButton.png);
background-repeat:no-repeat !important;
background-position: 0 0 !important;
}
.ui-picklist-button-add-all{
background-image: url(images/addAllButton.png);
background-repeat:no-repeat !important;
background-position: 0 0 !important;
}
.ui-picklist-button-remove-all{
background-image: url(images/removeButton.jpg);
background-repeat:no-repeat !important;
background-position: 0 0 !important;
}
.ui-picklist-button-remove{
background-image: url(images/removeAllButton.jpg);
background-repeat:no-repeat !important;
background-position: 0 0 !important;
}

styleClass="ui-picklist-button-add-all ui-picklist-button-remove ui-picklist-button-remove-all ui-picklist-button-add"

In this case the original icon appears on top of new image and the new image is placed additionally in the upper left corner of the page.