After translating enough extra pages that mention the site, I decided to sign up back in May. With the basic service, you get to download stuff like standby displays (Flash and non-Flash, monthly calendars), ring tunes from the movies/anime, play games, and much much more. And they keep adding stuff every week.
There’s a separate pay-per-item site as well. I got a Hachi “dress-up your keitai” item which is a set of Flash standby/call receive/email send & receive/alarm screens, as well as customized menus to access your phone functions. The battery meter is a strawberry (of course!), and a Hachi dog sits by your antenna reception meter. Kawaii yo!
You can check out both sites from your PC via here.