As I was searching up for more Yahoo! Messenger libraries to piece up the post-auth packets sent (I’m THAT close to getting YMSG9/10 up and running completely), I found a link to a site portfolio of a person named Brian Kobashikawa who worked as a UX designer for Yahoo! Messenger from 2002-2005. If you scroll down a bit, you can also see a screenshot of Yahoo! Messenger 5.5 in action. But I just wanted to show this off because this is honestly a cool discovery.
Link to said person’s site: http://www.kobash.com/portfolio/?id=ymsgr