With new tools to create 3D objects and game scripts, and the import of tons of creation from the original TrackMania, Stadium is a title rich in creations! Check the official wiki and forum to learn more and get started!
I was expecting there to be a pretty good variety of Press Forward tracks in the Workshop. Sure, there's no challenge to them (on my end), but I like watching them. And no, unfortunately, I don't have the skills necessary (or the time) to make any myself.