I want to give Linux a go and would like to have it look like this desktop here.

http://www.gentoo.org/images/shots/edon-tux.png

Its Gentoo Linux with a gnome desktop but none of that means anything to me.
I would like to download gentoo linux and then install the gnome desktop but then how do I actually get my desktop to look like the above? Is it some sort of theme and if so where would I find it?
Also would Gentoo be okay for me to use as a begginer.
Thanks.