I just have installed Ubuntu 12.10 (fresh new installation) and installed an icon theme pack - Nitrux Icons - and everything is fine, except the battery icon in the system tray. Here's the icon with the charge adapter unplugged:
And it looks fine - that's the real icon. But when I plug the charger it shows as:
Thats not the real icon.
Also, with other themes like Faenza - it shows the same icon when the charger is plugged in.