Read a lot then! And be prepared for a lot of head scratching!
Basically, check out gKrellM for the part on the left showing disk activity, network activity, date / time, mail, etc; fbdesk for the icons, though i'm not a fan; icons on the menu by manually editing your menu file; transparent terminals for the processes in the background.
There's tons of stuff on these forums, just do a search for fluxbox. There are also quite a few answers and quick tutorials, certainly on transparent terminals, menu icons, and desktop icons.