Of the two choices, I think stars would look cohesive.
But I had a 3rd thought. What about a series of narrow (1.5-2" finished) borders in solids, alternated with black, in maybe three of the colors from the quilt? In other words, add to what you have there by doing black/yellow/black/blue/black/light green? Your quilt has a sky theme to me--rainbow stars, and I think narrow borders in a few rainbow colors would give it a modern flair and be a simple finish to boot!