Is it possible to swap an image with another image, so I can try different images in a motion capture without having to set up the motion capture again and again for each image?
Yes. In View / Window / Project Media, find the target media event and R click that event. In the context window that opens, click on the "Replace" option which will open an Explorer window where you can drill down to the folder/event with which you want to replace the original event.
You could add additional images as takes on the event. You can right-click the media in the media pool and choose "Replace" and pick a different media. There's definitely ways to do this.