This is Fluxbox v1.0.0 with the “sid_fluxarnation” style, running on top of Slackware 12.1. I don’t recall where I got the sid_fluxarnation style, but you can easily find one like it, among about a billion others by going here or by following any of the other links in the “styles” section at the bottom of this page on the Fluxbox site.
As always, if anyone has questions regarding how to configure or tweak their Fluxbox setup, let me know. It’s easier than you might think! Cheers!