I can assure you that the seizure triggering aspect of "snowfall" on a screen is no joke. I've not used that feature, but my wife--who has more disabilities than you can count--has to be extremely wary of anything that flickers. The movement seems to sort of hypnotize her, and if she doesn't realize what's happening immediately, the flickers take over and down she goes.

I've been her caretaker for the past 17 years and have become hyper vigilant when it comes to anything presenting repetitive, unsought motion. Even a flickering fluorescent light can wipe her out in a hurry.