How to add background Video on a component

As it is not possible to attach properties to CSS values like the background video url, what is the recommended solution to make this configurable when using a component?

In my example: I am building a Hero Stage which should habe a video background, but i just cant get it working. I managed to add a new control to the section, where the URL can be configured, but obviously the backend preview doesn’t show the video. In the frontend it works fine, because i also updated the render() function to use my new control field for the URL.

Any tips here?