A quite successful practice making cinemagraphs, which is a video that's been masked over with a still from that video. This creates an eye-catching movement at the focal point, without the file size of a full video. Cinemagraphs make a great image for use in social media or websites due to the quality "video" combined with that smaller file size. One can also be seen as the hero image of the main "What I've Done" page here on HinterDesign!
Video converted to animation in Photoshop. The video is cut down to 3 or 4 seconds, then duplicated in reverse. This allows for seamless transitions back and forth, allowing for a never-ending animation.