Oh, people can definitely post other works that aren't just Pokemon, whether they're for other fandoms or original works.
As for recommendation threads, every once in a while, someone might make a thread in the Writer's Lounge subforum asking for people's recommendations. Most people post Pokemon fanfics, but some people post for other fandoms. It's just more difficult to recommend fanfics for other fandoms because it needs to reach fans that not only like that fandom but also Pokemon in order to be here.
So there's no official thread for recommendations, but if you feel like making one that can encompass all fanfics and not just Pokemon ones, you can. And maybe the mods will decide to make an official one that's more organized.