Hmmm, good questions and if I think about it then I would most likely prefer Original world, not that far from RL, with some fantasy aspects if needed. From what I would like as themes then I enjoy a bit of everything....Probably I would like to join in every of those themes but what scares me is that I do not possess the right amount of knowledge to be able to write in detailed story. And I kind of have a thing of talking really widely so I would probably go with a paragraph at least, in worst case scenario 3-4 sentences.
And I have one question. Many years ago I tried something similar and I joined the game and what annoyed me was that someone starts like a private conversation or just asks a question and the puppet master of the character that the question was asked to is not replying for many hours(work, school or anything else) so people just kept writing. So my question is what to do in such situation? Ignore that any question was asked and just jump in where everyone is? And what if the story has gonet that far that you need almost to make up a new story about yourself to be able to join back in from where you were absent...?