I would have to concur that you should have a drain drop at the end of the line on either side, but that should be all you need in a two-car garage, IMO. If you were plumbing a much larger shop that had a high-volume usage and multiple user points on each wall, as all the diagrams you posted show, then you would need more.

As far as putting in all those expensive unions, I don't believe those to be necessary. You should sketch out your actual needs and then only put a union where you feel you might have to make a major disconnection in the future. Even most production shops that are plumbed for air do not have all those unions due to the cost and relative non-necessity.

And yes, you should be able to reduce the pipe diameter to 1/2" for the actual drops. The 3/4" main lines are to give you the continuous volume you need to run more than one line at a time. This is assuming that your compressor has the air volume capacity to run two lines at once.

Above all, don't go all Samuri on it and K.I.*.*.

Thanks lash ,BillBoost37, Darrel and bastard, you've all given me good advice. At the moment though this garage is driving me to drink. I'm in the process of building angle iron channels as well as angle brackets to hand some metal wire shelves to the wall. I have to be absolutely sure it doesn't fall off the wall or else I'm in a heap of trouble. I'm hoping they will hold 500 ibs. each.

You know what, I just realised that I'm doing a garage makeover and I'm going broke........wait..............I'm already broke.

Which corner is the toolbox going in? I'd suggest an air drop there as well....although you said 50ft from the ceiling right?

Forget it.. That'* more than you need already. When does the lift get installed?

I'm going to have 2 toolboxes going accross the rear left corner of the garage. One air hose will be 50' long and the other will be 150' long.
I wish I could put in a lift but no budget since I was hoping to stay married and no room.