Why don't you look deep down, think, and then write from your heart whatever you please. That's how I do it anyway.
Romance between a high class pureblood vampire engaged to someone but falls for a human (boy or girl)
But then you will keep coming to other people for inspiration and then it won't be your story anymore. It will be ideas mushed together by other people to make your story. Bakuman had a similar thing going, and the guy that was doing that just failed miserably at manga after most of his "council of 50" dropped him. You need to have a general story planned out in your head. But I'm quite sure you wont listen to me though, but that's fine. Ranting about this helped me a bit actually. Weird right?