well on my old servers i used to hold alot of events so here are some of them
find the gourd: hide the monster named gorud then ask everyone to find it while u give some clues on where it is
monster tower: spawn monsters on big ben in NLC and ask everyone to kill it
silver slime town: spawn alot of silver slime in 1 small place
horntail in fm: as the name says a horntail in fm
lynn's farm: well lynn is my friend and likes to make so called "bob farm" so i usually rally some players to raid her farm and we like it...(just spawn some monsters and bobs)
all around maplestory in 30 mins: ask everyone to get some etc item from all around maplestory in 30 mins