You can customize the Windows 7 desktop using the default tools. The new Display dialog offers different options, but the choice is limited. If you are not satisfied with the default wallpapers, screen savers, and other display items, you can always customize the Windows 7 desktop using Windows 7 theme packages.
By default, Windows 7 has plenty of beautiful wallpapers that you can even set to change at regular intervals. It offers you the ability of making all the full screen windows transparent at the click of mouse so you can see the gadgets on your desktop. Windows 7 did away with the sidebar so that you can place your Microsoft Windows Gadgets at any place on the desktop. Even with all these excellent features, people tend to get bored and wish for something that suits their tastes. For teens, more often, it is to show off their notebooks. This is where Windows 7 themes help to customize the Windows 7 desktop.
Windows 7 themes are packages that contain one or more wallpapers, different colors/fonts for Windows and Desktop elements (such as the taskbar, start menu, and quick launch), screensavers, sounds, etc. Note that Windows 7 themes may not contain all of the elements described. One package may only change the desktop and default colors while another may include screensavers and sounds as well. It depends upon the person who creates the themes and that can be anyone. Even you can compile a set of images, screensavers and other stuff and upload it onto the Internet so that others can use it. You do need to explain how to install the screensavers. Hence, it is always a good practice to include a text file in the theme. It explains installation of different elements to customize the Windows 7 desktop using your theme package.