Forum:How to correctly refer to images in Wikia.css?

I currently refer to my images like this:

.jmw-switchboard { background-image: url( http://images4.wikia.nocookie.net/jadeempire-modding/images/4/45/Switchboard.png ); /* ... */ }

Is this the recommended/easiest way or should I do it differently?

(url(File:Switchboard.png) doesn't seem to work...)