I think you have a great idea. Use black sashing and it all will be fine. It will be interesting to have a quilt for yourself made with one of each block that you have used in other quilts. That's even better than using your scraps in a quilt. You will be able to see and tell friends and family about each block. The recipients of the quilts will recognize 'their block' in your quilt. Go for it!
I have pictures of each quilt and scraps of the fabric used. Sometimes I will write a little about the journey of making the quilt.