First, the things I've noted that events have aside from decorations (not all have these):
-Quest Chains
-Masks
-Special NPCs
-Random Event Drops
-Summoning Stones
-Tonics
-Mini Games
-Miniature Pets
I think these should be spread to all of them. Those that don't have these, can get them. I also have individual suggestions for events:
Canthan New Year
What this event has:
-Quests
-Random Event Drops
-Miniature Pets (Celestial Pets, new every year) and Greased Lightning
-Hats
-Mini Games
What this event needs:
-Special Tonics (Become a <enter animal here>) - this can be done, as the finale turns us into said animal.
-Summoning Stones (Summon a Celestial <enter animal here>)
-Last longer (One weekend to One Week)
This event is nearly without need for improvements. It only is missing a Tonic, and is a little too short. Summoning Stones - only in the Wintersday event at this time *the only event after widespread Summoning Stones in GW*has these, so not sure if they will become a multi-event item like Tonics, Hats, and Minipets.
Birthday Celebration/Day of the Tengu
These two events, one discontinued, the other minute. The Birthday Celebration, what we currently have, only has:
-Special NPCs
-Special Event Drops
-Mini Games
The Day of the Tengu had quests and masks *therefore an actual finale*. These are things the Birthday Celebreation lacks.
What I suggest for this event is to bring back the Day of the Tengu, merging the Birthday Celebration into it.
This leaves the following missing:
-Tonics
-Summoning Stones
-Miniature Pets
All of those can be Tengu items. A Tengu Tonic, a Tengu Summoning Stone, and a Tengu Mini. The Angchu Tengu would probably be the best to use.
Merging the two events would also allow those who didn't get the Tengu Mask to get a new version of said mask. There is also very little need for merging them, since the info from the Day of the Tengu should still be in the .dat file.
There is only one change needed from the Day of the Tengu: Change the Naga Fangs to Victory Tokens.
Dragon Festival
This event, like the Canthan New Year, is a really fun event and needs little to improve it. But it does lack some things.
What is present:
-Special NPCs
-Special Event Drops
-Mini Games
-Hats
What is missing:
-Tonics
-Summoning Stones
-Miniature Pets
Aside from adding those three things, I suggest one thing:
Being able to choose between Demons winning and Demons losing. In other words, if the "demons" win, you get the new Demon/Grasp Mask. If the "demons" lose, you get the new Dragon Mask.
Mind you, not the old Dragon Mask. And it doesn't have to be a Dragon Mask, just more Canthan based, not demon based.
International Talk Like a Pirate Day
Yes, I know this is not a "real" event, but since prior to my suggestions, Cantha gets 2 events, and Tyria/Elona gets 2 events, and after my suggestions, Cantha will have 3 events, I figured Tyria and Elona deserved a third event.
As such, I suggest adding NPCs, quests, a tonic and whatnot based on Corsairs. This is also lore supported - as there are in fact Corsairs in the southern parts of Tyria (around Orr). The finale could be a Corsair invasion.
Another thing, making this an holiday would make the perfect excuse to bring back the "Party Time!" affect from the Farewell to Gaile event.
Things in specification to add:
-2 Quest Chains (one in Tyria, one in Elona)
Tyrian: Idea - stop a Corsair threat-Corsair Tonics: Turns you into a Corsair (just take the mechanic from the Blacktide Den mission)
Elonian: Idea - help Margrid/Shahai out or stop a Corsair threat (if latter, go with the idea of a "full out war" brewing *aka a Third Great Corsair War*)
-Corsair Summoning Stone: Summons a Corsair
-Mask: Corsair Garb
After the first year - if GW1 continues after GW2's release (or GW2 isn't out still) just give the same idea as the Dragon Festival, a reenactment.
Halloween
A truly wonderful event. But also a truly lacking event. Especially in comparison to Wintersday.
Halloween doesn't have a quest chain, all others that currently exist (taking Day of the Tengu instead of the Birthday Celebration) have quests. This is truly sad.
Linsey said that she would work on getting the Teller of Tales in for Halloween 2009. If so, we can get quests given by this Teller of Tales.
But Halloween is also missing:
-Miniature Pet (Mad King Thorn Guard mini pet anyone?)
-Summoning Stones (same as above for what)
Wintersday
There is only two changes needed:
Add a wintersday chest at the end of the other two Rift Warden quests (the ones that go into the Underworld) and
Increase the drop rate of the MPB - no need for super rare mini pets this late in the game.