I like your enthusiasm Awesome.
Typically people post their pre-production work here relating to a specific project that is already in progress. Like a rough draft or completed script, or maybe a storyboard or set building in progress, either for feedback or just for people to follow along. It sounds like you're looking to brainstorm new ideas, so why not call this thread "New Idea Brainstorm Thread"? Who knows, there might already be an appropriate thread for that?
While you're working on coming up with a story idea, why not create some simple tests like walking, jumping, maybe a simple fight?
Also, browse around these forums a bit more, you'll get an idea of how things work, and you'll find there are little challenges that might be a fun way to get some practice in, and maybe a little inspiration.
I know there's a cartwheel challenge currently on, I'll let you enjoy exploring the forum and find it