Advice:

 The costume can be something very unusual like a superhero costume, something

traditional like a 旗袍, or something just a little out of the ordinary, like wearing a

suit if you don't usually wear one.

 Your unique costume could also be a chance to use some high-level or specific

vocabulary - for example, the names of superheroes. Alternatively, you could

research how to describe a pattern or material to impress the examiner.

 Halloween is an excellent topic to discuss when you wear a unique

costume.