Currently main is all that is offered. It has been discussed with the hosting provider to allow a user to accept responsibility to add other repositories, but I have not got this done yet.
So at the moment neither backports or other repositories possible. Also before to many additional options, cgi-frontend was dropped in debian-next branch (5.x of live-build.git), so it needs to be debianized on its own and I would like to get it included in debian main.