This feature is being rolled out to Facebook pages from May 2017. You can now add movement into your Facebook cover photo by adding a video (mp4) file.
Have you got the feature yet? You will know if you have the option to add a video as the camera in the top left of the cover will flash with an alternate old style video camcorder icon. Simply click the icon and select that you wish to upload a video.
In preparation, here are the specs to comply with for your video:
* Video length: 20 – 90 seconds
* Video Dimensions: 820 X 312 pixels