How to change ubuntu logo icon of left application menu

[mylinux2012]

Hi Guys

i use Ubuntu 11.04 Desktop Edition and I have edited grub.cfg but
I would like to change ubuntu logo icon of left application menu with my own one.
Another one is how to customize the gdm and usplash with my own.
Then when I installed remastersys to make own distro, I could not install it properly.

Thanks alot