So maybe I didn't have enough of the bright cats on black after all. Apparently I had to lay everything out to figure that out. However, another excavation into the stash found the bright cats on black fabric on the left. In the spirit of the fractured quilt, I slit the "too small" backing along the diagonal and inserted a panel of the new fabric to create a fractured back. That sounds much worse than it is.
Vicki W.'s blog.