I held onto the three painted canvases for a while, trying to decide what to do with them. I knew I wanted some texture on them, but that they would probably not be able to support having anything heavy glued directly to them.
I ended up deciding to wrap them randomly in white raffia, and for one of them, the yellow one, I also glued that air clay flower I made earlier to the raffia. I painted the flower first, because the white clay got stained and dingy as I worked with it.
I tied the raffia behind the canvas, rather than gluing it down, so if I ever change my mind, I can remove it easily without damage to the canvases.