Assuming you've properly fed, watered and trained your internet community, it should grow it's own culture. Usually stemming from inside jokes or central ideas (like a YouTuber or streamer that your community is based around ). It will grow itself just from people interacting and silly things happening. It will be unique in it's own right, just from the people there and the things they do. You can of course influence this by the things you say, the things you post and how often you do these things. If you do these often enough people will associate you with them, and by extension your community. (They don't call me Pepsiman for nothing). In regards to scale? The smaller it is the faster it will define itself.
In summary, the best way to grow a culture is to feed it while it grows itself. The best thing you can do is bring in more people to give it room to grow. Your internet culture is defined mainly by what you do and why you do it.