It's awesome that you're going to write a story in one of the fandoms I requested. Basically, I hope you write a story that you can have fun with, because Yuletide should be fun. But to give you an idea of the sort of story I enjoy, what follows are some of my likes and dislikes, as well as my original prompts.
Things That Make Me Happy
I love angsty stories and hurt/comfort. I love banter. I love competent characters behaving competently. I love scrappy little guys who never give up. I love plotty stories. I love character studies. I love happy endings. I like unhappy endings, if they're of the magnificently tragic variety. I prefer slash, but like gen. I'd even be willing to read Damiel/Marian het in Wings of Desire or Lizzie/Peter in Wimbledon, but would prefer no het in my other requested fandoms. With slash, it's the emotional intimacy that matters more to me than the physical, though I wouldn't turn down some rousing physical intimacy. While I most want to see the characters listed, I am fond of seeing other characters in the fandoms and how they interact with the guys I love best. And I'm not averse to OC's, if they're well drawn and essential to the plot.
Things I Can Do Without
I'd prefer no non-con or rape. I do not get crack!fic, or song!fic. I dislike seeing competent characters acting stupidly, or strong characters made into whimpering children. I'm iffy on BDSM and most kink. I never used to get Mpreg, but have recently found that I'm okay with it in Take That if it's Jason having the baby.
And here are my specific requests:
Take That: Mark, Howard, Jason, Robbie
For obvious reasons, I wasn't sure I was going to request this fandom this year. But it's still the fandom of my heart, and the current situation plays into my love of angst, so here is my request.
First off, if you want to deal with Jason leaving the band, either to fix it or explain it, I'd love to read it. The thought of TT3 makes me a bit sad, but I could go with it. (Howard comforting Mark is an intriguing possibility. Or vice versa.) My preferred era is probably TT4, but I enjoy either version of TT5. I adore wilderness years fic. And if you want to get away from canon, I'd love any AU you can throw at me: steam punk, musketeers, SF AUs in the Kidz spaceship would all be awesome. Wherever and whenever you set the story, I'm awfully fond of hurt/comfort. I love whumped but strong Mark, strong but vulnerable Howard, smart and vulnerable Jason, and unexpectedly sweet Robbie. My pairings of choice are Mark/Robbie and Howard/Jason, though I'm also fond of Jason/Mark/Howard.
Wings of Desire: Damiel, Cassiel, Marion, Nick Cave
I love the push and pull between Cassiel and Damiel, the way Damiel is willing to throw himself into mortal life, while Cassiel feels intensely, but can't quite make the leap. Maybe a vignette set after Damiel crosses over, with Cassiel following his friend. Maybe a story set when they're both still angels, possibly during WW II. Slash not necessary, but not unwelcome. And a guest appearance by Nick Cave would be awesome.
Strike Back - Damien Scott, Michael Stonebridge
A series that hits my competency kink. I love the professionalism that Scott, Stonebridge and the whole team bring to their assignments. I love the connection between Scott and Stonebridge, and the way they react when one of them is injured. I'd love some hurt/comfort, especially if it's Scott looking after Stonebridge. (I love the way the big lunkhead reacts when Stonebridge is in danger.) I'm okay with gen, but would also love to see slash. Maybe have them confined somewhere waiting, with Scott having no one but Stonebridge to expend his sexual energy on. I also love the women of Section 20, especially Richmond, and would love to see her involved in any story.
Wimbledon, Peter Cold, Dieter Prohl
I like Lizzie, really I do, and her and Peter are rather sweet together. And yet I also really want to see Peter end up in the arms of Dieter. This is partly because Paul Bettany and Nikolaj Coster-Waldau are very pretty together. And partly because they just have such wonderful chemistry. So if you could find a way to somehow throw Peter and Dieter together, I'd be eternally grateful. Perhaps some back story on how they came to be friends and a bit more. Perhaps a time they let competitiveness slide into something else. Or if you want to write in the time of the film, a little OT3 action wouldn't come amiss.
That's it for the specifics. In the end, I hope you write something that gives you joy. That's sure to bring me joy as well.