Very impressive. :) There's at least one element that changes occasionally, I've seen both Chiyo-chan's "father" and Ena's actual mother peering around the doorframe at her towards the end. I'm not sure if anything else changes for sure or not, but that one is very obvious. :)
Some of parts of this flash change when you watch it repeatedly! Once when Fuuka was hanging in the window Asagi wasn't there, but she appeared next time I watched. I thought that might be a bug, but then the scene with Ena's teddy bear totally changed the character that showed up from Chiyo-dad to Momma Ayase!
Chiyo Chichi is definitely in here, so I added him. Early on there's someone who looks suspiciously like Chiyo too, but I'll let someone with faster eyes decide on that one.
