You're welcome. "L" copper should be fine. Remember to size your main air header large enough to supply all the tools you may be running at the same time - and go 3/4" or 1" MINIMUM header to 1/2" taps. Even in a small shop, a 1/2" pipe many times won't keep up with two air tools running at the same time.
Just some links on why NOT to use PVC for compressed air piping. (You got me thinking...) ABS, however, can be used provided the pipe is marked approved for such use by the manufacturer. I'd shy away from plastics in above grade installations, if for no other reason the possibility of physical damage.
http://torque1st.clubfte.com/OSHA_PVC_Pipe.htm
http://www.osha.gov/dts/hib/hib_data/hib19880520.html