Here are some poorly photographed sashing options. I only have a little bit of the plaid for demonstration purposes (more can be acquired). This will be tough because the plaid will need careful cutting so that it is straight. It may drive me cuckoo, but I like the colors. I’m also not sure this will work with the scrappy border that will be added.
Here’s a tried and true favorite, red Roman glass. I think this one may be the winner. What do you think?