I really am curious, because the closest thing we get to a centerpiece is a bunch of miniature gourds my grandparents grew and sent home with me months ago, which are now covered in globs of paint courtesy of four out of five Crislers. (Yes, I painted gourds, too. I have to keep my inner 4-Her satisfied somehow.) And they don't scream "centerpiece" so much as "way station before their eventual destination: the garbage."
An added benefit to this style of "centerpiece" is that now I have a kitchen that is 25% more colorful than it was this time yesterday, because there is almost as much paint on the floor as there is on the gourds. Not to worry; it scrubs off easily, which is why all art projects are undertaken on the kitchen floor rather than at a table like fancy folk.
The best part is that none of this would have happened if we didn't have an Atticus who requests special art projects on a near- weekly basis, and who also insisted the finished product be put in "I don't know, like a bowl, or one of those jars that we keep the Band-aids in? And can you put them on the table so we can look at them every night at supper?"
Do you think Martha has an internship? One specifically for seven-year-old boys? Because I can only come up with so many craft ideas, and I'm running out of gourds...