In picture number 1 the VirtualBox dashboard is shown with the 3 running computers
Picture number 2: The desktop of the head node (left) and the two computing nodes (right)
In picture number two a PBS job executing a simple MPI task is demonstrated. The head node is on the left and the two computing nodes are on the right.
My general impression is that this Virtual Cluster is an excellent tool for education where the teacher and later on the students can experience Parallel Processing using their own laptops fairly easily.