Peony garden

Well, I have finally figured out where in the yard to put the peony garden that I have been wanting. We have an area that is defined by rocks which is way overgrown with big ugly shrubs that my husband wants out of there. So I found someone who is going to take them out for me and that's where I'm going to put the peonies. What else should I put there that will look nice once the peonies have stopped blooming? I prefer plants that bloom in pastel colors. On the other side of the bed from the rocks, the area is defined by a low boxwood border. There is already a butterfly bush (which may or may not be allowed to stay but will probably get a year's 'trial' and a pretty soft looking small tree that has scented white blossoms in the spring.

Thanks,
Gwendalou