The first thing I would like you to do is not stress. You and I signed up for this fest for exactly the same reason: we really, truly love female characters. That's enough to guarantee I will like your story. Please write something that YOU will enjoy and that YOU feel good about writing.
I love stories about awesome women, but "awesome" doesn't have to mean a perfect woman kicking ass and saving the day. I think it's awesome to show a sympathetic character with human flaws, or to find something relatable in a woman who's usually the villain. I love stories about women who are competent and in charge, but I also love stories where tough ladies are vulnerable or quiet women save the day (even if they weren't sure they could do it).
Some of my favorite stories are back stories, character studies and slices of every day life. I love hearing about the things that make an extraordinary character human -- like, what are her little rituals, her habits, and her quirks? What does a bad morning look like for Cersei Lannister? Do the women of SHIELD ever have to pick up their dry cleaning, and how do they fit that in around thwarting alien invasions?
I love gen fic just as much as shippy stories. To me, they're not really that different -- friendships can be just as complicated as romantic relationships, and I love to see characters working through the challenges of each. While I don't like to read about outright dysfunctional relationships, I do like stories where characters have to solve a problem with each other. I also really like stories where women are physically or emotionally protective of men. Bittersweet endings are welcome, but outright sad ones not so much (unless it's Game of Thrones, in which case, everything is sad).
My list of dislikes is pretty small. I'm a pretty vanilla fangirl, so no hardcore kink please. Sex scenes are fine so long as they advance the plot or characterization somehow. I don't really care for anything that would be described as "crack," and I'd rather not receive a wacky AU where all the characters are in high school/in a rock band/working at a bakery etc. I trust your discretion about rape, incest, and graphic violence -- those things are pretty par for the course for a fandom like Game of Thrones, but they would definitely not belong in the world of Brooklyn Nine-Nine.
A few fandom-specific notes...
Agents of SHIELD: If you're writing about Agent Hand, I'd love to see a more sympathetic side of her. I can't believe she's *just* an unfeeling rule follower. If you are writing a shippy story, I think May/Ward is super interesting, and FitzSimmons are adorable platonically, romantically, or anywhere in between.
Brooklyn Nine-Nine: I quite like Amy/Jake, but I don't really like Rosa and Amy paired together.
Game of Thrones: As mentioned above, I can handle potentially disturbing content in this fandom if that's where your story takes you. I have NOT read any of the George R.R. Martin books so please please please don't spoil me for anything that isn't in the show.
MCU: Tony/Pepper is my OTP. Please do not break them up or write them as outright dysfunctional (working through a problem in their relationship is fine).
Sleepy Hollow: I like Jenny/Irving, or friendship fic between the two of them is fine. I like seeing her relationship with Abbie, and seeing how her friendship with Ichabod develops. Please do not pair Ichabod with anyone other than Katrina; I just don't think he would cheat on his wife.