NB! It seems this console command is not compatible with CS2.
Command Profile

MAP_BACKGROUND

CS:GO

This command will make the specified map become the background of the main menu. May not work since Panorama mode (new CS:GO UI).

Syntax
map_background [Map Code]

Description

This command will make the specified map become the background of the main menu. May not work since Panorama mode (new CS:GO UI).

How To Use map_background

  1. Enable the developer console in Counter-Strike settings.
  2. Open the console with the tilde key (~).
  3. Enter map_background [Map Code], replacing bracketed arguments with the value you want, then press Enter.

This legacy command is not currently listed as compatible with Counter-Strike 2.

Syntax And Arguments

map_background [Map Code]
Map Code The map code of the map you wish to set as the background of the main menu.