I just added a swfdec plugin to decode Flash SWF movies. It supports transparent backgrounds so you can composite it over video. Good animation tools are hard to come by, and a lot of people know and like Adobe Flash Builder. If you, a friend, or colleague likes to use Flash Builder or After Effects to design motion graphics, now you can easily use their animations. Also, the Qt-based animation tool Pencil can export to SWF, which you may find more manageable than an image sequence.