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.
If you go to the bottom of iwaku you'll see some headlines. "About us", "site functions", "Useful links" and "support iwaku!"
Under "Site functions" you can see the text "request thread moderation". Click that and send in a thread move request :)