span.customcheck {
  background: url("../../img/checkboxes.jpg") no-repeat scroll 0 0 transparent;
  display: inline-block;
  height: 14px;
  margin-right: 5px;
  width: 13px;
}

span.customcheckfull { background-position:0 0; }
span.customcheckfull:hover { background-position:-13px 0; }
span.customchecknone { background-position:0 -14px; }
span.customchecknone:hover { background-position:-13px -14px; }
span.customcheckpartial { background-position:0 -28px; }
span.customcheckpartial:hover { background-position:-13px -28px; }