I'm not a novice at FMQ, but haven't done an awful lot either. That's a lovely quilt & my first thought was bubbles or pebbles as they're called. Just little circles all over. It creates a fun texture & would compliment the top. I would probably use a neutral thread unless you're more sure of yourself after practicing and then I'd use variegated purple thread! Beautiful either way!! Best of luck with whatever you decide!