I have this Arch system with GNOME that I made a couple months ago, the computer that it's on has 4 gigs of RAM and a triple-core AMD Phenom II. While I was browsing the internet bone day, I saw Arch systems that had the Arch Logo on the login screen in GNOME. And I was wondering how to do it. So if you could post the directions and commands needed that'll be great!

As a sidenote, I have a couple extra questions:
How can you install Unity on Arch Linux?
Is it possible to somehow install the dpkg and apt-get on Arch and be able to access the Debian repositories?