Virtual prototypes that can be turned into physical objects (but I'll only be dealing with the visual ones for my job)
creating two dimensional mock ups of a 3 dimensional object is possible but it sounds to me like you may want to consider programs like 3ds max or Mya.
those programs would allow you to create 3 dimensional objects that clients could "turn around" and see from all angles.
now, you can create skins in photoshop, import them into a 3d program and then skin your object.