You may do it by randomizing the shape keys values using a script.
Create some shapekeys for your model (change head, body and other body parts parameters).
In Text Editor window click on New button, copy the script from here: How to set a random value for multiple shape keys? and paste it to the editor window. As you can see, all the shapekeys values changed randomly.
Go to User Preferences (Ctrl+Alt+U) and enable the Corrective Shape keys addon.
In the Shape Keys panel click on the arrow icon and choose create duplicate for editing option. Now you have new unique mesh. You can create many of them very fast. The more shapekeys you have, the more combinations are there. Good luck :).
