I think placing the arty on the map is not a good idea.
First of all the arty was positioned far behind the front troops. Requests were given via radio or wire from special arty spotter over looking the front or from the commanders in the front directly.
Also it would be much work to place all statics needed to make a believable artillery battery position and then still look stupid if there are like 6 leFH18 shooting without any players around.
I read a few books with personal WW2 accounts and they all mentioned the psycho terror an artillery shells flying overhead causes. Not only when the are coming towards you, especially mentioned a few times were the slow 30cm German rockets from DO-Gerät. They seemed to put fear in your guts if you only heard them flying above you. (a deep slow frequency sound and low velocity).
Also the naval shelling on the battlefields near Memel and Königsberg must have been real psycho terror. 30cm shells made much noise as well when coming in and the impact blew everything apart.