Part of the point of this website is to ensure that the Architectural Katas don't die out due to lack of creativity on one man's part. Thus, getting community participation into the kata mindset is kind of important.
The easiest way to contribute is to take an idea you have for an architectural kata (whether it's totally made up, a project you heard a buddy of yours working on, or a project that you yourself are working on) and send it to us. Doing this couldn't be easier--clone the GitHub repository containing all the katas and post a PR. Or, if you don't like the website, post a PR to the website repo.
Alternatively, you could join the Google Group and post your kata idea, and we can iterate on it, but the group is pretty quiet and the PR approach is likely to get faster response. Any kata idea will often need some iteration/revision, and to protect any intellectual property concerns I often try to change the domain somewhat as well (if necessary or requested).
But if you're more the event-planner type, why not host one? All you need is a room capable of holding somewhere from 12 to 75 people, with rearrangeable furniture and, ideally, some whiteboards or notepads and such. If you can do it regularly, we'll see that you get some kind of Web-link love from this site.