Why do you want this quilt bigger? Will the added border be the drop on a bed or will it frame on the top of the bed? If it is to be a drop then I would pick a small floral as aeborder so it looks like the center is in a garden or maybe a light green so it seems like you are looking through treas to see the "scene" To make it about 12" larger that means 6" on each side. I think that it needs no other borders especially if you are going to use it as a wallhanging or as a small quilt.