What I think makes this an attractive arrangement, aside from the uniform color theme, is the variation on plant heights and bloom shapes. There is vertical interest (Veronica and Perilla), there will be something tumbling over the edge of the pot (Creeping Jenny), and in the spaces in between, I'll have the Impatiens and the Verbena. For the most part, it conforms to the "recipe" I learned about from reading an article in Fine Gardening magazine a while back. The recipe brilliantly but succinctly captures what many successful container gardeners have put into practice for quite some time and that is the concept of "Thriller, Filler and Spiller". Think about it: you want one plant that has vertical interest and is the focal point providing drama to the entire arrangement. Then you want to plant some spilling and trailing plants to soften the edges of the container. Finally, you'll need to fill in the remaining spaces with plants that will serve as sort of the supporting cast of the mixed planting, giving it depth and dimension.
This little tip was well worth the price of a full year's subscription as far as I'm concerned because I think about it and put it to use every time I plant a new container.
Bookshelf: Container Gardening Books