Description from the official Costume FAQ:
- Costumes are items that are equipped into a character's costume slots to change their appearance. Costumes are decorative items only. They are worn over a character's existing armor without affecting any stats.
There are slots for costume headpieces and body pieces in the inventory window. A single body piece dresses the whole character's body, except the head, unlike normal armor which is broken down into separate pieces for different body parts. Similar to guild capes and headgear, costume slots have toggles that can be set to show or hide your costume in combat areas or towns and outposts. Costumes are automatically hidden during PvP matches.
There are two categories of costumes: full costumes, consisting of matching head and body pieces, and festival hats. Unlike armor, those costumes pieces that can be dyed are usually not dyed gray by default; the default colors are noted in the individual articles. Most full costume pieces can be dyed, most festival hats cannot be dyed.
 Full costumes
Full costumes can be purchased through the Guild Wars In-Game Store or the NCsoft store. They are released two or three sets at a time, themed for an in-game event, and can be purchased individually or for a limited time as a discounted combo pack.
|Set||Head piece(s)||Body piece(s)|
|Wintersday 2009||Dwayna's Regalia||Dwayna's Diadem||Dwayna's Regalia|
|Grenth's Regalia||Grenth's Visage||Grenth's Regalia|
|War in Kryta||Shining Blade Uniform||Shining Blade Cowl||Shining Blade Uniform|
|White Mantle Disguise||White Mantle Mitre||White Mantle Robes|
|Halloween 2010||Lunatic Court Finery||Lunatic Court Helm|| Lunatic Court Finery|
Lunatic Court Headless Finery
|Raiment of the Lich|| Aspect of the Lich
Cowl of the Lich
|Raiment of the Lich|
|Hearts of the North||Wedding Couple Attire||Wedding Headpiece|| Wedding Finery|
Traditional Wedding Finery
|Formal Attire||Formal Headwear||Formal Outfit|
|Dapper Tuxedo||Dapper Top Hat||Dapper Tuxedo|
|Wintersday 2010||Agent of Balthazar||Horned Helm of Balthazar||Balthazar's Doublet|
|Disciple of Melandru||Melandru's Helm||Melandru's Vestments|
|Winds of Change||Dragonguard||Wisdom of the Dragon||Soul of the Dragon|
|Aegis of Unity||Unity of Purpose||Unity of Spirit|
|Halloween 2011||Ravenheart Witchwear||Ravenheart's Gaze||Ravenheart's Clutch|
|Vale Wraith||Wraith Veil||Wraith Shroud|
 Festival hats
Festival hats are costume headpieces handed out as a reward during seasonal special events. They can be "registered" at a festival hat maker by showing it to him, and he can then create that hat for all characters on your account.
Most festival hats cannot be dyed. Those that can be dyed are marked with an asterisk (*) in the table below.
|Lion's Arch||Kamadan||Grenth victory||Dwayna victory|
|2005||Pumpkin Crown||Horns of Grenth||Yule Cap|
|2006||Dragon Mask*||Furious Pumpkin Crown||Wicked Hat|| Great Horns of Grenth (LA)
Jester's Cap* (Kamadan)
| Stylish Yule Cap (LA)|
Freezie Crown (Kamadan)
|2007||Demon Mask||Scarecrow Mask||Mummy Mask||Ice Crown||Wreath Crown|
|2008||Grasping Mask||Zombie Face Paint||Lupine Mask||Grentch Cap||Rudi Mask|
|2009||Imperial Dragon Mask*||Charr Hat||Skeleton Face Paint||Ice Shard Crest||Snow Crystal Crest|
|2010||Sinister Dragon Mask*||Furrocious Ears||Spectercles||Demonic Horns||Divine Halo|
|2011||Mirthful Dragon Mask*||Tricorne||Reaper's Hood|
|Other||Lion Mask* (every Canthan New Year) • Tengu Mask* (Day of the Tengu 2006)|
 Image gallery
The costumes marked with an asterisk (*) have alternative looks, click on the individual galleries to see them.
|Dwayna's Regalia||Grenth's Regalia||Agent of Balthazar||Disciple of Melandru|
|Lunatic Court Finery *||Raiment of the Lich *||Shining Blade Uniform||White Mantle Disguise|
|Dapper Tuxedo||Formal Attire||Wedding Couple Attire *|
|Dragonguard||Aegis of Unity||Ravenheart Witchwear||Vale Wraith|
 Festival hats