beastytee: creepy evil laughing trees ! Halloween wont the same without some of those

Give the game a darker shade to get into that halloween feel

Oh and of course! As mentioned by a lot of other players add a halloween appearance

froggy: A new area, only open in October, called House of Horror. Random mobs from the necro area spawn, but are more powerful, and give out better items.

Or, you could make a bunch of buyable costumes, allowing people to change their head and body. Make a costume store. Sell some costumes for credits. Some for gold. Getting to change your character's sprite in a variety of head and body combinations would increase sales. Of course, you'd have to add a Costumes tab, and make them removable.

kirigaya_yueki: Pumpkin item in the bag for everyone as a gift. .

astrazeneca: Make a -jack- pumpkinhead smilie

zyxs: Waiting Halloween Round. ^_^

delance: create a halloween appearance,

change some monster with Halloween clothes or create new Halloween monsters, more skeleton and flying bat in decorations,
new Halloween smiles,
new quest monster,
new crafted gear with halloween themes,

new lord monster "a mutant pumpkin" will appear after killing blackdragon, a special prize for killing it : like a death angel scythe and titled pumpkin lord