There are endless plant combinations depending on your preferences, whether contrasting plants or colour themed. With plant combinations remember when putting ideas together, to check flowering times. Even between varieties of the same flower, the flowering time can greatly.
For example, this image shows a combination of grasses with Allium. Alliums are known as a late spring flowering plant, but for this combination it is essential to pick one of the late summer flowering variety of Allium, such as Allium sphaerocephalon, which is illustrated.