In general, I like fics that either emulate the style of the source material or that work to subvert that style in an interesting way. For stories not building on fictional sources, I enjoy those that attempt to have the characters thinking and acting like people from the time periods and cultures in question, rather than as modern, usually western, people in historical costume. I love happy endings, first time stories, stories about friendship, adventure stories, introspective pieces, comedies and angst! You see, I really will be happy with whatever you write! I love AUs and crossovers, if you're struck by one of those (my LJ profile should give you a hint as to the fandoms I know). As for what I don't like, non-consensual sex and sex with children written as erotica and graphic harm to children and animals are not my fictional cup of tea.
If you'd like a little more information about what I like in the fandoms I asked for, here's what I enjoy about them:
When William Came: The interesting thing for me about this is that, despite the long, long speeches in which various people discuss What Various Classes/Ethnicities Are Like, the narrative basically shows that the speeches are wrong. The German characters shown are all humane and almost as much caught off-guard by the sudden change of events as the British, a working class character is the only one who listens to the endless talk and then actually does something, the narrative indicates that Hohenzollern Britain is one that gives Jewish culture more breathing space and so on. The ending of the novel and the greater political world are somewhat sketchy, but they leave great open ares for what happens next fic, or what is happening in the greater empire fic. (Although the British court has fled to India and the empire is supposedly still loyal, the only apparent fighting force that can be raised is from Canada - what is really going on in the rest of the empire? What's going on in the rest of Europe, for that matter? An unnamed visitor from the Austro-Hungarian empire shows that not everyone in Europe is terribly pleased with imperial politics generally). If you're writing this and would rather focus on the general setting and world-building rather than the nominated characters, that would be just fine!
(Sign-up optional details: One obvious thing is what happened next? How were the scouts treated for their disobedience? Or a story looking at Cecily and Murray's relationship as his realisation of his acceptance of the fait accompli really sinks in. Or perhaps Murray discovers to his horror that he has become friends with Leutnant von Gabelroth (or more, if you'd like to write slash). Does Cecily ever discover an interest in politics? What is von Kwarl doing as time goes on? Anything you'd care to write would be wonderful!)
Hut 33: I just love the madcap humour of the storylines, the very funny (and deliberately terrible) jokes and the use of the 1940s to comment on the present day. I enjoy the class warfare between Charles' snobbery and Archie's inverted snobbery, Josh's never-ending dimness, Gordon's never-ending innocence. Most of all, I love Minka. (Oh, Minka). The more Minka the better, really, she's just great.
(Sign-up optional details: I'd love a comedy story that kept the somewhat surreal feel of the radio show - do the staff of Hut 33 discover a famous man Mrs Best *hasn't* slept with (is such a thing even possible)? What terrible plan does Archie and/or Charles come up with this time? What's Minka's life story this week?)
Daughter of Mystery: I just love the world-building of this novel (and its sequel, The Mystic Marriage): the way Alpennia fits into the greater European politic scene of the early 19th century world, how its language seems to work as one of the many smaller European languages, the way in which its society seems to be holding on to a past that other countries have moved away from. I like the way in which the women characters are portrayed as negotiating around the restrictions placed on them, and the way in which their faith, their theological and alchemical studies and their friendships and loves are treated utterly seriously.
(Sign-up optional details: I'd love something that perhaps concentrates on the world building of the book(s) - how does Alpennia fit into early 19th century European politics and culture? Or something about Barbara's training, or more about her and Margarit's theological study would be wonderful. Or perhaps something on Antuniet's alchemical work as she goes from city to city, or how Jeanne negotiates Alpennian society, protected by her wealth and widowhood!)
Saki’s short stories: Anything, dear writer, anything! I just long for a Clovis story - cross him over with another fandom (either Edwardian or not), send him into space, whatever - just let him be Clovis (appallingly frank, as Saki said, and malevolently amused at others' expense) and, hopefully, let him live.
(Sign-up optional details: I love the light, malicious fun of Saki’s stories, their sometimes surreal and always pointed satirisation of the time. I especially love the character of Clovis Sangrail and his terrible (for other people) sense of humour. Whatever you’d choose to do with this prompt would be wonderful - I just want there to be another Clovis story in the world: crossovers, AUs, anything would be welcome here!)