Many people use and like the grid view in iTunes, where albums are shown in a grid layout and can be played individually instead of having the songs of all albums in one big list. Unfortunately Apple does not provide a way to customize the background in the grid view, and in the latest version of iTunes people are forced to use the new white backdrop to their albums. This has not been a welcomed change by some people, who wish to still use the darker background.
There have been several methods posted around the internet on how to change iTunes back to a dark background, but recently a small installer has come out that implements these changes to the program automatically. It is available here if you care to give it a try: http://chaodam.frenchlabs.net/themes/dark-grid-mode-for-itunes-9/
Keep in mind that this does alter the iTunes program, and could lead to unexpected behavior in the program. As such, be sure to back up your iTunes library and other iTunes support files before applying this or any other modification to the program. Unlike other OS X applications that may need to be reinstalled from the OS X installation DVD (sometimes requiring the use of Pacifist), iTunes can easily be reinstalled if any problems occur.