Before Eureka Seven: Hi-Evolution 1 was announced and released, or even before Eureka Seven: AO, there was a Japanese website for Project Eureka hosted by one of the artists that contained all of the concept art for Eureka Seven, as well as art from other projects of that artist. I thought the website was EurekaSeven.jp, but Wayback Machine shows this to be a new URL, not the old website from 2006-2008.
The one with the concept art didn't have flash, or if it did it was only in the header. It had a beige textured background. I thought it was Kenichi Yoshida's old website. A cursory glance through my bookmarks and I couldn't find it. I'm hoping someone else remembers what I'm talking about.