Well, I won. So I had to pick a scenario that I'd find sexy.
I'm still on a Skyrim kick (and still a furry), so I wanted something with a Khajiit. But I didn't have a particular preference for a male vs. female Khajiit. I realized I'm turned on both by the idea of being held by fur-covered arms and having those fur-covered arms. But either way, I wanted the Khajiit to be the dominant individual. They are predators, and it is exciting to be either the hunter or the hunted.
When determining what kind of story to write, Ume asked me an interesting question: how intelligent did I want the Khajiit character to be? More animal-like, human-like, or superior to humans? I decided I wanted the Khajiit to be at least as intelligent as a human, but with strong instincts to hunt and pursue. It's that marriage - that fusion - of human cunning and animal desire that I find so entrancing and so arousing. It makes them even more dangerous.
I also didn't really want any explicit BDSM themes in the story. No dungeon setting, no crops/floggers, no chains. Those are a very tactile, physical appeal to me; just thinking about them doesn't do it. I have to be actually experiencing them. However, the mind games involved in bending someone to your will - or, conversely, in getting your will slowly get broken and overpowered by a good dom - is something that does turn me on just by thinking about it.
I'm interested to see what Ume comes up with. He decided he wanted to give the story a more modern setting, so it won't be purely a Skyrim fanfic. I'm also getting the urge to try writing my own erotica. I've tried before, but I've never been able to finish a story; either I feel too incredibly awkward to write out the sex scene, or I get so turned on by it that I start fapping furiously, and then I forget.