Historical, fantasy, magic, horror, supernatural, survival, vampires, demons, pirates, mutants, ghosts, romance (FxF, MxM, MxF) (Romance should be part of the plot and not the whole plot in itself), etc.
Since you ask so nicely here's some links ;) If you want to find one x one partners then you go to one x one requests and start searching there by either posting a new topic where you ask after partners or by answering on others requests ;) If you are into mature stuff then mature requests is a good place ^^ (That section is about to change now so don't forget to read the announcement about the changes.)
For group rps there are modern, fantasy and sci-fi sign ups, where you can either post your idea or read others ideas and join in.
You can also jump into an rp in the jump in section or do your own jump in roleplay, no bio is required if the GM hasn't said anything else. And at last, in roleplay talk you can discuss a idea you have and see if someone is interested before you post it in the modern, fantasy or sci-fi section.
Also we have a general chat where you can chat a lot :) And you can join groups to find people that share the same interest as you ;)
Hope you find your way around on iwaku and if you have any questions about the site then it's just to ask in thecommunity hub or an admin (people with blue usernames) ^^