Edit: I am aware of the fact, that this was only a suggestion and not a voting poll, but some of the "contra" arguments seemed very... weak to me. :/
Doability also plays a role. "Pirates" and "Horror" may sound like fun ... but there's not much you can do in a hotel to actually make the theme recognizable, and there's not much budget for decorations. So the casino theme is a good choice from an organisational standpoint ... since casinos are often also hotels, it nicely reflects the change we're making from this year's location. And we can achieve a certain recognizability even with little effort, because a hotel already is a fitting background for a casino theme.
Maybe another theme would have been more popular, but then, what would it be worth if the con book cover would be the only thing you could recognize it from? So we're playing it safe.
And of course I can't decide a motto that most of the staff hate. No matter how popular a theme would have been in a poll, if it's totally uninspiring (or even annoying) to the more important creative heads among the staff, it'll create frustration, which will end in a bad execution of things, or even general demotivation. And believe me, keeping the staff motivated is harder than you think, and dependant on stuff you wouldn't expect. People take this very personally, it's not just a job
So ... I'm not meaning to argue. But this is the honest explanation, why we didn't decide on a Pirate-Furence or a Horror-Furence. These themes just didn't inspire anyone, they felt old and overdone, and trying to do them anyway would probably have ended in a failure because of that.
