I love the name
Wren. I'd stick with
Wren because Wrenna looks odd. If you do like the sound of Wrenna, I'd suggest
Irena (prn 'ih' (as in 'eagle' ih-renna). It's my mother's name and Polish.
Irena Firenze sounds pretty nice to me.
I also love
Mei.
Cecily Mei is absolutely gorgeous.
I also really like
Ming as a mn.
Cecily Ming also has a nice ring to it.