Yes it is possible, people use Cardboard for test benches as they dont short out the Mobo.
In fact, I think there is a project log somewhere on Toms where somebody did this as a testbench. The Mobo was attached to a peice of thick cardboard much like it would be to a normal Case, and the cardboard was upright. They were using a huge external Rad and watercooling. It looked awesome, there were decals and drawings allover, and the cardboard ended up looking immense with the designs.