I wouldn't change a thing! First of all you have done a great job in selecting fabrics with good contrast. The stars pop just fine and don't need quilting to enhance them other than what you have shown (the simple echo inside the star and the meander right up to the seam line). The only thing I can think of that might emphasize the stars more is to SITD around them. IMHO the effort taken to do so would not result in a payout significant enough to bother.
Do not switch to a dark bobbin thread. Every wobble and mistake will scream like a beacon at you.
Keep going with what you are doing. You are 2nd guessing what are obviously great quilting instincts.