The more I looked at iris, the more I was inclined to agree, there really isn't a big open space in the middle, it's filled with all sorts of little petals/reproductive parts. It seemed quite confusing actually, and I had a hard time finding good clear pictures. I finally settled on a style arm with an anther underneath it; botanists and gardeners, apologies if this is all wrong.... The style arm looked mostly like a smaller petal, while the anther looked sort of stick like and fuzzy.
I made my style arm out of leftover pieces I'd painted and quilted for the large iris, and just sort of shaped them until I was reasonably happy. It was a bit tricky, since I'd recently cut up all the big scraps from the project thinking I was done with it, but I found enough pieces. For the anther, I stitched a bunch of layers of batting around a piece of wire and fluffed and fluffed and fluffed and then painted. This was the first version, which was ok from the standpoint of the little petal, but the size, fleshy color, and general protrudingness of the anther made it look way to much like an inappropriate body part, especially in person. It really jumped out at you in a quite incongruous way.
So I trimmed it down and reshaped it and repainted it and now I think it looks much more like a flower innard. I like the way there's now detail inside but it doesn't overwhelm the shape or impact of the large petals.
I'm still not sure I'm completely sold on it, but it'll continue to live there on the wall and if I get inspired, I'll change it up some more.