I am building a spare room in our garage. I am going to be dry walling over our main electrical service above the circuit panel. Is there anything I should do to protect the wires from puncture behind the wall? I was thinking a sheet metal plate from the top of the box to the ceiling? If anyone has any ideas, or who have done this before I am anxious to your thoughts.

No special protection is needed for the cables in the space between framing members. Any cable attached to the studs on either side must be 1-1/4" back from the face of the stud, if a screw attaching the drywall to the stud misses the stud.

Good measurements of the framing and careful installation of the drywall screws is needed.

If plumbing or something else causes you to be closer that 1 1/4", you can use these:
Halex 62899 1 1/2 By 2 1/2 Nail Plates #6776603 at HardwareAndTools.com (http://www.hardwareandtools.com/Halex-62899-1-1-2-By-2-1-2-Nail-Plates-6776603.html)
If you have a Large picture and know where the nail/hook? Is going to be, you could nail in a piece of 2 X 4 for support.