lindy, I like your thinking and agree that it could be good to put in a darker border to separate the cream from the white. I also really love the simplicity of this and how it very nicely frames the center. Please don't stress. Sometimes these only need a simple addition to be the perfect touch. No need to overcomplicate. And FYI, I'm very easy to please. ;)
I'm also on plan B for Mary's center. Plan A was too busy and competed rather than complimented the center. This one I think will be just right but might be a couple of days before I get a chance to finish it. Very full weekend here.