th.header { 
    background-image: url(/img/jquery/tablesorter/bg.gif); 
    background-repeat: no-repeat; 
    background-position: center right; 
}
th.headerSortUp { 
    background-image: url(/img/jquery/tablesorter/asc.gif); 
}
th.headerSortDown { 
    background-image: url(/img/jquery/tablesorter/desc.gif); 
}