For an August wedding, I would go for a more open, lighter shoe. Perhaps work with the white color.... or clear. And the necklace should probably be more airy, as well. It will give a feeling of summer breeze...Perhaps some type of "floating pearls -- or a simple silver chain with a light green pendant
Black is great, but if you are wearing a basically black dress, you need to lighten it up a bit for a summer function.
All in all, though - very sexy indeed!