j0hnik,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
.slider {
width: 100px;
height: 200px;
background-image: url(http://images.vectorhq.com/images/previews/013/christmas-tree-psd-413028.png);
background-size: 100px 200px;
background-repeat: no-repeat;
}
.r:checked ~ .slider{
background-image: url(http://file.mobilmusic.ru/11/54/a5/952948-400.jpg);
}
</style>
</head>
<body>
<input name="r" type="radio" checked="checked">
<input name="r" type="radio" class="r">
<div class="slider"></div>
</body>
</html>