Some Linux distributions put a lot of time into making sure that their default desktop looks pretty. Others do not. Either way, you don't have to settle for the included artwork in a distribution! Plenty of options exist on the Internet to find more icons and backgrounds for your computer. Here, I will focus on finding Linux specific content, as well as how to participate in the online community of artwork content creation.
Linux Artwork Repositories:
For years, I have enjoyed looking at the different artwork available for making Linux beautiful. The first site I visited was kde-look.org, which focuses on creation of eyecandy for the KDE desktop, in the form of wallpapers, themes, icons, screensavers, and other desktop related content. Even though I don't currently use the KDE desktop environment, I still peruse the fine wallpapers available here.
Little did I realize at the time that kde-look.org is actually a part of the larger opendesktop.org project, which provides many opportunities including creating and sharing applications as well as artwork.
The artwork-related websites under the opendesktop.org umbrella include:
apps, as well, but that does not pertain to this topic. Check out opendesktop.org for more info on that.
KDE-Look.org Artwork for the KDE-Desktop
GNOME-Look.org Artwork for the GNOME-Desktop
Xfce-Look.org Artwork for the Xfce-Desktop
Box-Look.org Artwork for your Windowmanager
E17-Stuff.org Artwork for Enlightenment
Beryl-Themes.org Artwork for the Beryl Windowmanager
Compiz-Themes.org Artwork for the Compiz Windowmanager
EDE-Look.org Themes for your EDE Desktop
Debian-Art.org Stuff for Debian
Gentoo-Art.org Artwork for Gentoo Linux
SUSE-Art.org Artwork for openSUSE
Ubuntu-Art.org Artwork for Ubuntu
Kubuntu-Art.org Artwork for Kubuntu
LinuxMint-Art.org Artwork for Linux Mint
Frugalware-Art.org Artwork for Frugalware Linux
Arch-Stuff.org Artwork and Stuff for Arch Linux
So, you've found cool desktops, downloaded them, and set them as your personal wallpaper. Like the image, but hate the color? Change it! Many of the images and artwork that are released on these content sites are released under permissive licensing agreements that allow you to modify or create existing content for your own uses. For example, all of the artwork in this post has been either created or modified by me, and posted to kde-look.org, gnome-look.org, or ubuntu-art.org -- I used the GIMP, the GNU Image Manipulation program, to create and modify the images, then created an account on the site, and posted the images. Make sure you respect the license of the original poster. My user name is zooot if you wanted to search for my posted work.
One word of warning about these sites: There is no content filtering on these sites, so you may find pictures of ladies in various states of undress from time to time. Avoid that if you find it offensive or inappropriate. The sites do allow you to rate the artwork that is posted, and filter out any results that are under a particular score (usually 30%) if you desire.
In conclusion, a vast array of artwork is available for you to use to beautify your Linux distribution of choice. Take advantage of it! Better yet, make artwork and share it with others!