Overview
If you want to change the Left 4 Dead background to another Left 4 Dead background, come here.
Changing the Background
To do this you must go to:
Local Disk (?:) > Program Files (x86) > Steam > steamapps > common > left 4 dead > left4dead > media.
Here you will see the main menu backgrounds. They are the original, The Last Stand and Crash Course. Whichever one is your default must be renamed as something else. Then you can rename one of the other two to the default one’s original name and then that will be your L4D Main menu background. My default was l4d_crashcourse_bg.bik. I changed the name to l4d_cc.bik and changed my Last Stand background to be called l4d_crashcourse.bg.bik. To get the loading screen, you must have no file named as l4d_crashcourse_bg.bik.