Well one way to have a cool clown costume is to have a scary cool clown costume. Why not? Costumes aren’t just for kids so why not make it more adult while we are at it.
There are plenty of freakshow clown costumes online if you know where to look for them. Further, why not be even more original than that? You can be the scary server from hell–only you are dressed up as a clown in addition to this. Or if you are a stickler for the circus and still want to be more original…why not dress up as a scary ringmaster?
Or there’s Horns the Clown. When in doubt you can get ideas from clown horror movies. IT is far from the only clown horror movie out there; there’s everything from Mr. Jingles to a clown movie that Eli Roth did. Look thru them and take what you like and go to the Halloween store and build your own costume. No one says you can’t get a regular clown costume, cover yourself in fake blood and buy a Jason knife from the Halloween store either; or many other things but you get my point.