This page uses a video for the background image. This is designed for ONE PAGE ONLY, not as a site-wide option. Code snippets included.
Notes on video embeds:
Video on a website can be a bit tricky so there are no guarantees that the provided code will work with your video.
Most mobile devices do not autoplay video, so iOS and Android will just show the poster image.
IE8 and below will not show anything. There is code in the theme to try to overcome this, but IE8 and below are not supported.