I could do this though it is a whole lot of hand work and it would be obvious that they are sewn on top of the seam, not into it. I have FQs left of several of the fabrics that I could back the "points" with.
Instead of going that far maybe just use fabric crayons
(or whatever they are) and paint something around the edge. That probably wouldn't be as obvious that it was done after the quilting.