You know, I tried to do the same but it didn't work. I went looking for these icons to 'snatch' using the gpe filemanager, but can't seem to find the right ones.

Now, thanks to another thread about changing the startup screens, I found some in usr/share/icons/hicolor/scalable/hildon/ but swapping these out didn't change the left-side icon display. I rebooted a couple of times but no luck.

BTW, I did search and tried to find the info in this thread, but it's running 40+ pages and I just couldn't find it in all that...