When adding a sticky post (rotating or pinned) it would be fantastic if we could set an end date when it will remove itself.

This could be expanded to remove itself after a fixed amount of views, a percentage of the DAU's, etc. A minimum of X days could be set in case it reaches this value faster than anticipated.

This could be further expanded by scheduling when they're active. Post M is displayed every Monday. Post T every Tuesday, etc. Or a post could be displayed 8am-4pm and a different post from 4pm-8am. These could be pinned or rotating.

Lastly, unique sticky posts. Serve up pinned posts/rotating posts to specific users. Serve X post to users who have blocked a feed maker, have certain labels connected to them (a warning perhaps?) or fun messages intended only for those with a certain label. The sky's the limit here and I'm sure folks would find very creative ways to use this feature, maybe even make a feed based around this entirely.