Так?
<!DOCTYPE html>
<html>
<head>
<script src="https://code.jquery.com/jquery-latest.js"></script>
<script type="text/javascript">
$(document).ready(function (){
$(':radio').click(function (){
if (this.checked) {
$('#test').attr('src',this.value);
}
});
var sel = document.querySelectorAll('input[type=radio]')[0];
sel.checked = true;
$(sel).click();
});
</script>
</head>
<body>
<img id='test' src='http://javascript.ru/forum/images/smilies/blink.gif' />
<div>
<label>
<input type='radio' name='scr' value='http://javascript.ru/forum/images/smilies/smile.gif' />
Screen 1
</label>
</div>
<div>
<label>
<input type='radio' name='scr' value='http://javascript.ru/forum/images/smilies/wink.gif' />
Screen 2
</label>
</div>
<div>
<label>
<input type='radio' name='scr' value='http://javascript.ru/forum/images/smilies/laugh.gif' />
Screen 3
</label>
</div>
</body>
</html>