After catching up with this season, especially last night's episode, I am itching to try Klaus against my Caroline here. I'm not entirely sure what I want to do with them, exactly, but it can get fairly dark (I like the idea of him manipulating her and being the "dominant" one in their relationship, causing her to somehow depend on him). I don't have a whole lot of limits kink-wise, though I can gladly write up a short list of my hard-no's if you are curious. As for the storyline, it can follow the events of the show or it can be AU (so long as they remain vampires and he is still fairly evil).
I have no AIM, so everything would have to be managed through journals. I am willing to play her against other characters from the show, or even pb her if that is desired, but I would probably sell my soul for a long term Klaus.