The world is your oyster really. You want things that are going to take dry conditions so why not go for things like lavender and rosemary, they will provide some fragrance as well, as would things like sweet peas, stocks and nicotina (the older varieties are best) whose perfume could waft back into the house. They will need some support to stop them breaking in the wind. Boxes look good with something trailing from them. Trailing ivy will give you some foliage to go with the flowers, and then there are trailing geraniums (nice and tough), lobellia, snapdragons etc and why not think about some of the small grasses that can be grown in containers and will rustle in the wind. Many of them change colour from spring through to autumn. Hope this gives you some ideas to work on.