Default [Q] Changing files that change back.

Well basically all I want to do is change //res/images/charger/battery_charge.png but everytime I change it, match the permissions and change the owner to match the other files then i power off and plug my charger in but then it comes up with the default charging picture and when I boot the file has changed.

Could anyone please tell me if it's possible to do that or if it will just change back and if it is possible how would I do it?

The device I am trying to change it on is a Nexus 7 V2 Wifi.