Not much to see from the top so here is the underside of this shelf pattern. Simple scrolled brackets, leaf pattern under the shelf and a 6" deep shelf.The pattern is designed so you can adjust the length of the shelf. The one in the picture is 16" long. You could take this up to about 30" before the proportions would start to look odd.
I used 1/2" walnut for this shelf. I also used a cove bit on my router to under cut the shelf on the front and sides.
I love working with walnut. It cuts great, finishes well and is not too expensive. That's a pretty good combination.