Higher English creative folioWatch
Maybe think about how many characters are in your story? Can you be medusa?
Remember the point of the folio is not to write a "good" story, it is to write a piece with clear story line, but more to show your application of different writing techniques and ability to building real depth of settings and a character to immerse the reader, so try to pick a story that will allow you do this.
I had to do creative last year for my Higher folio, which I originally hated (wanted to do persuasive, but we only did one folio piece and this was the style of writing the teacher concentrated on), I was really stuck with this and my teacher suggested writing a story about just walking through an art gallery. I thought that was a terrible idea, but gave it a go and it developed onto something very different, in the end a very simple story with more depth worked very well and I got 14/15 (doubled up to 28/30).