table.dataTable thead .sorting {
   background-image: url('../image/sort_both.png');
   background-repeat: no-repeat;
   background-position: center right;
}

table.dataTable thead .sorting_asc {
   background-image: url('../image/sort_asc.png');
   background-repeat: no-repeat;
   background-position: center right;
}

table.dataTable thead .sorting_desc {
   background-image: url('../image/sort_desc.png');
   background-repeat: no-repeat;
   background-position: center right;
}