You might have noticed a new setting on this screen: Repeat Sequence. This setting will repeat the entire sequence as many times as desired. A good example is a walk-cycle, or some animation that needs to repeat. Of course, the more times you repeat a sequence, the longer the video clip will be.
Remember, any folder with numbered images can be imported using this feature. Using a nice image editor (such as InkScape), it's easy to play around with your own "flip-book" style of animating. Just save each frame of your animation, and when you are done, drag one of the images into OpenShot. Enjoy!