Randomized Backgrounds In Garry's Mod

In Half-Life 2, Portal, and (Before the Mac Update) Team Fortress 2, when you start up the game there would be a random background.

How do you have that happen in Garry’s Mod?

Well technically it’s not a randomized background or a moving one. It’s a map that loads and the menu is just laid on top of it. It’s been done with Gmod before but it has to go through a map loading screen to get to it. It’s not fun.