With our changing climate especially with all the rain in the UK last year, moss is a likely candidate as perfect ground cover in our yards.
This is a display box at Kyoto's Silver Temple in Japan showing a range of mosses that are used in the formal garden there. But I love the format of the display boxes which makes a superb feature in its own right - it would look great with a range of different saxifrages as well.
http://gardenista.com/posts/10-easy-pieces-the-most-magical-mosses