With html script tags (apparently this messageboard doesn't allow posting html tags).

# window.resizeTo(500,300)
as Footer.html in Resources did the trick.

Took embarrassingly long time for me to figure that out.

Oh you got it nicely done. I just modified Black is Beautiful theme for my liking and to go with this chat theme. I used the alternating from that skin and removed bubbles and disabled group to just show online users and its quite nice now. But I have a question about Adium chat window size (I don't like tabs), it keeps returning to some quite small size (400x300 or so) but I'd like it to be always one size and something like 500x300 or a bit more in width. How would I solve this?

Have you tried designing a userlist to go with it? Or which one do you use yourself?
It is very nice theme, probably the best in this site actually.