I suggest creating some unique content for it full of free Halloween Theme'd wallpapers, icons, pictures, anything a user could use for their website, social networking page. Do some seo, both on and off page, and then when Halloween rolls around next year you'll actually have a site that ranks, or have a site that is worthy of being sold.
I would agree with SCLocal, but if you were to sell as a domain only I think you could get around mid $xx in a reseller market or more if developed or sold to an end user.