TimelineJS jQuery issue needs fixing

I have built a Timeline using TimelineJS by [login to view URL] It is integrated into Wordpress using the JSON API so that it fetches posts and they appear on the timeline. I want the post featured image to render at full screen width (regardless of resolution) with the text positioned on top of the image. This must be possible because it is being done here: [login to view URL] I have analysed their code and they have been able to set their images as a background on a They then use some CSS to make it fill the screen: .media-bg { background-size: cover !important; height: 100% !important; min-height: 100% !important; min-width: 100% !important; width: 100% !important; }