I know the feeling, which is why some of my oneshots are over 10k words haha. I like long one-shots. But if it's too long or the story needs more explaining but not enough to be massive, make it a short story. They're always fun!
Well I finished one, which has been posted, and then I just have some others to work on, mostly Thorki ones haha. You should watch some movies or read something, it might help you come up with an idea :D