Here's a working example: http://jsfiddle.net/Gajotres/wL2gQ/
I hope that is what you've wanted.
HTML :
<div data-role="page" id="radio-icons">
<div data-role="content">
<div data-role="fieldcontain">
<fieldset data-role="controlgroup">
<input type="radio" name="radio-choice-1" id="radio-choice-1" value="choice-1" checked="checked" />
<label for="radio-choice-1" ><div id="custom-label"><span class="ui-icon ui-icon-bars ui-icon-shadow up"> </span></div></label>
<input type="radio" name="radio-choice-1" id="radio-choice-2" value="choice-2" />
<label for="radio-choice-2"><div id="custom-label"><span class="ui-icon ui-icon-bars ui-icon-shadow down"> </span></div></label>
</fieldset>
</div>
</div>
</div>
CSS :
#custom-label {
width: 18px;
height: 18px;
background-color: rgba(0, 0, 0, 0.4);
background-image: url("images/icons-18-white.png");
background-repeat: no-repeat;
border-radius: 9px 9px 9px 9px;
}
#custom-label span {
left: 45px !important;
margin-top: -7px;
}
#custom-label span.up {
background-position: -180px -1px !important;
}
#custom-label span.down {
background-position: -216px -1px !important;
}