Existing skins in the /Data/skins folder have the images for the stars, you should copy those into your skin folder and you need css something like this which is from one of the included skins:
.ratingcontainer { float:right; white-space:nowrap; margin:5px 5px 5px 5px; }
.ratingprompt { float: left; margin-right: 5px; }
.leftside .ratingprompt , .rightside .ratingprompt{ display: none; }
.voteswrap { margin-left: 5px; }
.ratingcontainer div { float:left; white-space:nowrap; margin:0px 0px 0px 0px; }
.ratingrow { white-space:nowrap; }
.ratingStar { white-space:nowrap; height:14px; margin:1em; }
.ratingStar .ratingItem { font-size:0; width:13px; height:12px; display:block; background-repeat:no-repeat; cursor:pointer; margin:0; padding:0; }
.ratingStar .Filled { background-image:url('ratingStarFilled.png'); }
.ratingStar .Empty { background-image:url('ratingStarEmpty.png'); }
.ratingStar .Saved { background-image:url('ratingStarSaved.png'); }
.ratingbuttons { margin: 0px 0px 0px 0px; padding: 2px 0px 0px 0px; }
.rcommentprompt { display:block;}
.ratingcomments { border:#000 1px solid; background-color:#eee; color:#000; width:206px; height:200px; position:absolute; margin-top:15px; padding:5px; }
.ratingcommentbox { width:200px; height:100px; }
Hope it helps,
Joe