Greetings MadMax, and welcome to the Story Teller's Circle.
You won't have trouble finding someone with the same interests, and you can post requests/ideas about your niche/genre at the Bulletin Board. As for writing, we pretty much have the full 360: Roleplays, Creative Writing, Discussion/Debate, Fanfiction, you name it. As gorey and action packed as you like, or as casual and lighthearted as you like. Note: Erotica (Detailed/dedicated erotic content) is not permitted, that is the only true restriction put in place for obvious reasons.
Before you can write, however, you will be in an "Introductory Phase" where you need to post a few times in main lobby to be approved. This is primarily to introduce you into the community, and let you know that you have plenty of writers to chat with or ask advice from. There is no time limit to being approved, and getting roleplays sorted out takes time anyways, so don't feel pressured to write a ton of posts in one night.
Now that I have described the community and system to you somewhat, and more specific details can be found in the rules page, I would like to know you better as a writer. If you don't mind, finding a roleplay is easy if we know the genres you enjoy. Mad Max and Batman are a sort of modern fiction theme (Low-Fantasy is the name of the genre), but do you also like Sci-Fi, Medieval Fantasy, Slice of Life, etc?
I look forward to seeing your work, and wish you luck in your spiritual journey as a writer, or whatever philosophical cliche you prefer.