Some hillside yards need terracing with rock or some other type of retaining wall. Rock gardens and the planting ideas used to create them offer a lot of opportunity for creativity regardless if they're on a hill or elsewhere.
Totally unorganized or meaningfully organized as in some Japanese gardens, the two elements of hardscape (rocks) and softscape (plants) can combine to create beautiful displays of color and texture.
The purple planting scheme and light colored rocks make a nice combination in this design.
This rock garden is also used on a hillside landscape as a tasteful way to prevent erosion. The large boulders placed periodically create terracing as well as flat areas for planting. The terracing and flat areas help slow runoff and allows proper saturation for landscaping plants and their roots. Of course, terracing can also be created using retaining walls which could also look quite tasteful on this hillside.