Don't you just love an all white garden? Some people think it would be boring, but it is so not boring and there are so many plants to select from. In the spring many ornametal trees have white blooms...dogwoods, cherries, and some types of crabapples. Then there are the magnolias, bridal veil and many other shrubs.
And all of the bulbs, including tulips and daffodils. You can have pansies in white, hydrangeas, lilies, roses, clematis. There are just too many to name all of the perenniel, vines, and annuals you have to choose from.
The thing that is most important to remember is that with an all white garden, you need variety of shape, flowering season, and structure to keep it interesting.
As in the garden above, borders are importent. Use boxwood, hostas, monkey grass, or any other low growing plants that will be uniform in height to contain your garden beds. They add a sense of order and draw the eye.
Don't forget to add a focal point, such as a fountain, colored pot, or sculpture to give the garden interest. Remember that it needs to look good in every season, so take into consideration the shape of the planting without their leaves. Interesting bark and shape are very important no matter what your color scheme!