you will not believe this, but i did a quilt VERY similar to this, except mine was rectangle, actually used dryer sheets for the foundation. i did a narrow black scrappy border, about an inch, then did multiple stripes with the strips. i know there is a name for it, but i don't recall what it is. the stripes would be horizontal on either side, verticle on top and bottom and on an angle in the corners. when i do use a border on my quilts i usually make them 1/2 the width of the block.