I hope we're spared from having too many people amble around as Trump or Clinton. From some of the stories I've seen, it would appear that we'll have a lot of superheroes, Star Wars characters (trending toward the most recent movie), pirates and witches. So, in other words, a typical year, with perhaps a few more Harley Quinns than usual walking the streets and seeking candy.
Here are a few old photographs of people dressed up in costume, starting with a pair of found photos that have no identifying information.
This next one is from the family archives. I don't think it's Halloween, per se, because it's dated May 1914. It features a large group of men, half of whom are in drag. (There are also, unfortunately, a couple of men in blackface, a practice that didn't start to disappear until the 1960s in the United States.) Apparently, my great-grandfather, Howard Horsey Adams, is in this group photo, possibly dressed as a woman.
Here's the whole photo (which can be seen in a larger version if you click on it), plus a few closeups...
Finally, because it's only fair, here's a photo of me dressed up for a Halloween party 20 years ago. I kind of miss that shirt.