I would also suggest considering what the space will look like at different times during the day. Do you need to be able to see clearly at night? Perhaps some good lighting might be nice.
The first feature is a berm. A mound created at one or a few points in the garden to create levels with plants in and around it. This will mitigate water runoff.
The second is a dry riverbed. This feature creates a visually appealing feature that when it is not raining looks like a beautiful work of art. When it does rain, the water is collected and begins to percolate into the soil.
The third is a rain barrel. This is perfect to connect to the gutters to collect the rain water. The water can be used to water the garden or for just about anything.The fourth is a rock garden in which in certain areas in the garden you would use rocks and gravel as mulch instead of wood chips.
The last feature is a planted swale. This feature create a divot in the center of the area that water can collect. It is filled with rocks and gravel with other larger rocks around.