I used a combination of different kinds of pears and apples as the place holders (I think this idea originally came from Martha). I made paper leaves, stamped guests names on them, and punched a hole so the leaf could slide over the stem of the fruit.
For the centerpiece I used a cornucopia I had had for a while. I used clippings from a tree in my yard around it. I think I combined some artificial fruit with real fruit (tucking the fake stuff in behind) and nuts, to give the feeling of abundance.
You can see the berries in the glasses, carrying on the theme. But what made this fun is that I used the theme to help determine the menu, as well. Nearly everything we made included some kind of fruit or nut in the recipe.