I am planning for Major, Minor, and "Whisper" Events.
Major Events would be minigames, large-scale Plaza events, store sales, etc. We plan to use a walk in / walk out for Major Events and random minigames where the center fountain in. The fountain will visually change to alert and attract people. These are announced across all the servers.
Minor Events would be stuff that just occasionally happens like a new vendor appears, a character appears, or the sand has new items to find with the metal detector. Basically stuff that just occurs that's smaller in scope. These are announced.
"Whisper" Events are events that are secret or hidden. The event system will show a hint as to what it is, but players will have to discover them.