This lovely idea is fresh from the site of Portland Nursery and what a nice idea it is. There are so many edibles that are beautiful to look at.
I always use sterile potting soil in hanging baskets and put in a few tablespoons full of water-retention beads. Be careful with those beads though. I've put in too many and the plants floated away. Soak them first and follow the directions for how much to use with which size container.
Also, hanging baskets will have to be watered every couple of days when there is no rain falling. A mulch on the top will help the top stay moist.
Basil is a great centerpiece for a hanging basket since it grows fairly tall. There are plenty of purple and red-tinged basils that would be pretty. A little garlic or green onions would be pretty there, too.
And, what about a basket completely filled with assorted basil? Wow would that smell good and love sun all summer? Varieties abound.
For fillers around the outside, parsley (flat or curly) would work. Calendula (pot marigold) has such nice flowers. Here in our area they don't thrive in the heat of the summer so if you live where summers are hot, go with the parsley or cilantro.
Spillers that trail down the sides of the container could be creeping thyme, or if your summers are on the cool side, nasturtiums.Strawberries would also make a fun addition.
Your choices of plants will completely depend upon what thrives in your area but no matter where you live there will be lots to choose from.
Remember to check out your local farmers' markets for locally grown plants that will do well.