Gtalk system files located where on device?

[Sphagnum]

I have the Nexus S and on my Gtalk application I have a friend that I would like to manually change the icon next to their name. I have googled around and found no easy way of doing this but was hoping that the friend's icons are stored as .jpg or some such file somewhere on my device and that I could manually swap the one that's in there for the one I want using File Manager. But I cannot find anything other than the .apk and the .odex files related to Gtalk. Is that all there is?

Any help greatly appreciated!