I don't get to participate in these because I don't have the software or the skill you guys have, but I do enjoy watching them, and I even participate in the vote from time to time.
I really enjoy it when the challenges are seasonally themed, and for this month since it's Halloween, perhaps it could fit into that.
Back in my home town, my block would have a contest for this holiday, and for christmas for the best decorations. Who had the best haunted house type of thing.
My suggestion would be to take your favorite bridge, weather it be the Constitution class, galaxy class, defiant, vorcha, bird of prey, which ever it may be, and decorate it for the holiday. The vote could be on whoever has the scariest "Ghost ship"