If you want to have a lot of images in your Pages document and they all need to be the same size and other attributes, you can use a variety of techniques to reuse attributes over tens or hundreds of images. This same technique works for Keynote as well.
As always an instructive video. I save my clip document in Templates.
Lots of excellent ideas, but the best seems to be the oldest—copy and paste. (Or duplicate)
Gary: too bad there's no way to name custom image styles. I'm imagining it can be difficult to chose the correct one if there are multiple custom styles.