Hmmm it depends what you want , looking back in years to come . Would part of you feel regret that you don ' t have the traditional bridal party photos ? I think costume is a lot to ask of people to be honest unless they have something in their back pocket they HAVE to go out and buy something . People tend to recycle wedding outfits , whereas Halloween costumes generally get trashed or bits get left behind in barshouse parties . As a rule I personally don ' t like dress codes which make people spend money . A good comprise would be have each chair in the ceremony set out with cheap costume bits , and ask guests to put them on as they take their seats . You know , fairy wings , pirate hats , capes , a few wands , deelyboppers , cowboy hats , crowns , animal masks . If you want it to be really halloweeny put a few fake severed limbs etc about . This plan also avoid people choosing inappropriate costumes I saw a sexy Oscar The Grouch costume a while ago . which is also a bonus !