It's quite charming exactly the way it is!
To your question:
Enlarging it depends on the how you plan to use this pretty little quilt. You don't say how big it is now, so I'm guessing you think it's a bit smaller than what you pictured in your mind. But if it's made for a baby/child's quilt or wall hanging, it's probably just right. If not, then go ahead and make it rectangular. i'd be very interested in seeing how you do it!