Linux allows you to customize your desktop using GNOME, KDE ,Xfce or a variety of other desktop environments.
One of the challenges with so much choice is that customizing your computer can become an end in itself.
For example Knoppix Linux has really cool startup and shutdown sounds that you (if you're a nerd like me) might want to use for your computer.
Does that make your computer any more useful?
No, but it might make it more fun to use - and you can learn more about how computers work by doing something simple like that.
To get those startup and shutdown .wav files I downloaded the Knoppix .iso (image) file, burned the .iso file to a CD, found the .ogg audio files, installed Audacity to convert them to .wav, used FileZilla to FTP them to my web server and then added the links to this blog post using a simple right-click extension for Firefox built by Phil Ringnalda.
Playing around with computers is the best way to learn their, and your own, capability - as you learn more you may find that when you have something you want to do (besides playing) it's a lot easier.