I prefer it with just the blue fabric border. I don't think it needs a stop border (the thin border) at all.
When I look at the first picture I see depth...and attic windows mimic real windows...with the blue fabric right up against it, it looks like it's more forward then the Spy squares, much like a wall and windows that we look out on the world at.
Do you have a spy glass? It's like a little door hole peeky thing. You can view the quilt through it and it makes it appear further away, it gives a wonderful perspective on the quilt and you get to see it with a different eye. I think if you could see it through one of those that the stop border is unnecessary.
That being said, it's your quilt and you can make it however you want, so please enjoy!!!