As you can see from the photos, I did decide not to do any filler quilting in the corners of this piece.
After trying two different fillers and having to pick them out, I just couldn't bring myself to do a third. If I'd had to pick that one out, too, I think the fabric would have fallen apart. I didn't have any of the fabric used in this one, so the binding is just another piece I had lying around and that I thought worked okay. This will work as a table topper, as it's fairly small: only 17" square. Below is a detail of the quilting, though I apologize for the color being off.