Expansion Chambers

I am installing a new shower valve. Should I install expansion chambers on the hot and cold 1/2 copper water lines near the valve?

A shower usually doesn't need it, and if it does, expansion chambers are old school, and never worked very well for long - they quickly become waterlogged and are often impossible to recharge. If you need hammer arresters, put in the real thing. Sioux Chief and others make them. these are either a bladder or a sealed piston chamber that will stay dry and working for many years. Think finger over the end of a straw...once full of water, the end stays capped, they rarely drain and thus are useless.