Those items are called via their window manager names.
fluxbox_initmenu, ...
blackbox_initmenu, ...
jwm_initmenu, ...
And new is _setbackground which will work with control panel Backgrounds button.
You will need to wait for 2.0rc3 to become public and then all the window manger suport will work.
The TC Team is helping me find the final bugs. Currently being tested fluxbox_, jwm_, and hackedbox_. So at the moment all of those are still in a state of flux. But very soon eveything will come togther. I am sure many will look forward to your contributions of fluxbox and blackbox. I will be happy to assist in making sure the iterface files will work.