The first parameter is the chapter number. The second parameter is the name of the background.
You can add more "chapters" as much as you want.
And have whole different background names instead backgroundxx
It's important that the background name match with background texture (*.vmt).
Or you end up in this, missing texture
The game is loading the background texture from here, ...cstrike/materials/console/
For each "chapter" have to do two *.vmt files. Example
Which contains the path of your desired *.vtf picture.
(Which may be located somewhere else other than here in the same folder)
// Original shader: BaseTimesVertexColorAlphaBlendNoOverbright
// Uncomment this if you add an alpha channel to the base texture
// "$translucent" 1
"$basetexture" "dev/dev_signflammable01a" // Example
This far, different background images should be in action.
Edit the file ...cstrike/cfg/valve.rc
and add command startupmenu
// load the base configuration
// Setup custom controller
// run a user script file if present
// stuff command line statements
// display the startup level
There are a few things that prevent the background maps working.
You have -console or -dev in game launch options
You don't have map named by "chapter" background name (obviously)
Also, some background maps will not work as desired when the game starts in multiplayer mode.
Adding this cvar in launch options change the game in singleplayer mode.
Finally, what I have already mentioned a moment ago.
You need the background maps that is named after the "chapters".
The maps must be located at this path ...cstrike/maps/
example maps to above "chapters"