That is really cute!! So, you didn't say if you wanted it bigger. If it is good the size that it is - I would leave it as is and add a bright binding (my first choice) . But if you want to make it larger, I would be tempted to add a dark/medium blue border (to match the darker background of the stars) and bind it in a bright color. A blue border, imho, will frame it and not pull your attention away from the cute center and the bright squares.