I'm in to living history, sometimes known as reenacting. Cosplay for history buffs basically. The costumed party and walking around the streets stuff of halloween isn't that big here in Australia. It's growing in popularity, I think because of so much American media featuring it and it looks fun. The cosplayers I know, have mostly no objection to it and many will participate. We love to have opportunities to show off our work. So for many cosplayers, halloween would be a very big night in their costuming calendars, so I suspect that for many the opposite of your shower thought would be true.