Working example: http://jsfiddle.net/Gajotres/rQtmC/
CSS :
.ui-icon-alt li .ui-li-link-alt .ui-btn-inner .ui-btn {
width: 18px !important;
height: 18px !important;
border-width: 0 !important;
}
.ui-icon-alt li .ui-li-link-alt .ui-btn-inner .ui-btn, .ui-icon-alt li .ui-li-link-alt .ui-btn-inner .ui-btn .ui-btn-inner .ui-icon {
box-shadow: 0 0 0 !important;
}