Linux has many Window Manager such as KDE, Gnome, XFCE, fluxbox, or IceWM. Every Window Manager is typical. The only thing you need to make your Linux Desktop looks pretty is download from the Internet. Below is sites where you can download a lot of stuffs such as wallpaper, splash screen, or theme for your Window Manager.
1. Gnome - http://gnome-look.org
2. Fluxbox, IceWM, OpenBox, PekWM - http://box-look.org
3. XFCE - http://xfce-look.org
4. KDE - http://kde-look.org
fyi, I run Slackware Linux 12.1 on my computer and my Window Manager is KDE 3.5.7. Here is my GUI with kde-look's stuff.