按惯例先上一张展示图片
要实现自定义随机图片即在后台【页面定制css代码】添加一段简短的代码即可
body {
background-color: #efefef;
background-image: url(http://lorempixel.com/1600/900);
background-repeat: no-repeat;
background-attachment: fixed;
background-position: center 0;
background-size: cover;
}