Well, it's things like the People icon which I really don't need flashing around pointlessly. The weather icon I can understand but if I want a minute by minute update I'll look out of the window, and to get a look into the future you have to open it up anyway. You've prompted me to find the setting for that now. It was buried but there, so thanks for prompting me to be a bit less lazy.
The photo tile I'd already found the settings for, but the shortcut tiles to the few direct shortcuts to people flash about needlessly with no obvious settings. The Cortana tile seems to have no setting, and neither do those tiles showing a group of apps. But shuffling them off the screen isn't an issue.
Obviously you'd never want to stop the live tiles showing txts, calendar, emails, or missed calls, but they don't flap about annoyingly, just display a number or brief details.
One feature I do like, in a totally trivial aesthetic kind of way, is the way the little notification icons rotate when you switch from landscape to portrait. Shame the tiles don't rotate as well to allow landscape use, but all home screens seem to be standardised that way, so it's not a legitimate gripe.
Anyway, I now have a totally static home screen, with all the ADHD stuff hidden off the bottom. I'm slowly getting this thing set up to suit me!