Here's another example of using rock gardens to terrace a hillside or slope. In this idea, along with the plants, there are quite a few large boulders which are very dramatic. Proportion of elements is important here so as not to dwarf or hide each other.
In this garden and all gardens for that matter, it's important to know the MATURE SIZE of the plants you intend to use. Your plants and planting ideas are an element that will change so it has to be thought out.
This also a good example of a naturalized garden with a very wide variety of plants and grasses. However, in most true natural settings there isn't such a wide variety of individual plants. There is usually more repetition of single varieties. Using a lot of self seeding perennials will help rock gardens like this to fill in quickly and naturally.