Okay, I went through so many ways of doing this before I finally settled on one I think could work. The problem with multi-ship stuff is which do you include and which don't you? Does Xander/Faith have as much right to be included in the list as Xander/Anya? Of course it does - but will there be enough X/F fics to fill a category? Which is why I've gone for doing it like this.
There will be a Conventional Relationships category, and an Unconventional Relationships category. I will decide which belongs where - for example, in my opinion, we've seen enough Cordy/Angel on the show to make it conventional.
"But that's not many categories!" I hear you cry. Okay, this is where it gets weird. Once I recieve five fics for any one particular pairing, by at least two different authors, they get their own category. Then the unconventional vs conventional thing becomes redundant.
This way, I'm not having a category such as Buffy/Angel being empty because no-one enters B/A fic, and having a whole bunch of UC couples filling up one category when each ship could have their own.
I'm not sure how well I explained that, so if there are any probs, email me and I'll try and explain it a bit better!