content: url(...)

dabblet.css

/**
 * content: url(...)
 */
html {
	background: #f06;
	background: linear-gradient(45deg, #f06, yellow);
	min-height: 100%;
}

.container {
	border: 1px solid red;
	content: url(http://farm4.staticflickr.com/3069/2714790097_46155fd39f.jpg);
	display: block;
	height: 500px;
	margin: auto;
	width: 500px;
}

dabblet.html

<div class="container">I am a container</div>

dabblet.js

// alert('Hello world!');

settings.json

{"view":"split","fontsize":"100","seethrough":"","prefixfree":"1","page":"css"}