I mentioned, earlier this week, that I have finally gotten around to rewriting my simple background switcher so that it actually works under Gnome 3. At the time I was intending to tidy up the code a bit first and then push it all to the master branch.
Well, I haven’t gotten around to making the changes I intended (yet), but have pushed it to the Master anyway. The current development branch for MTB is 0.3 and, as soon as I have some time, I will see about making it all work a bit more generically.