Basically notes for the alliance, rules, tips, other that are always available to read. I would like to see if in the alliance description area where new members can read and all members can go back and refer to. The (Co)leader and elders are the only ones who can edit /add to the sticky notes.
It will be great if they implement the sticky notes , banner is supposed to be alliance motto or something that describe the Alliance. So its will be better if we have other tool than change the banner as sticky notes. My vote for your idea.
Once our rival in AW make the banner like this : Red tank. So their strategy is readable for us as their enemies, lol.