You can add your own textures for the boards. Uploading your own modifications to Steam.
To do this, declare a variable in any file exactly as in this file.
EXAMPLE LUA CODE:

SC_BoardStyles = SC_BoardStyles or {};
table.insert(SC_BoardStyles, { name = "MyCustomName", isAnimated = true, numTexture = 10, numDynamicElements = 15 });

* CONTINUED AND IN ENGLISH LETTERS ONLY, THE NAME MUST BE UNIQUE.

OPTIONS:
-- name - Required parameter, texture name.
-- isAnimated - Required parameter, is responsible for enabling or disabling dynamic textures in the background, as in "Default".
-- numTexture - Required if isAnimated = true, the number of different textures to create a dynamic texture.
-- numDynamicElements - Required if isAnimated = true, determines the number of generated textures. It is recommended to set values ​​up to 15.

* IMPORTANT. After creating the script in the same modification, place the board texture along the path:
/media/ui/boards/{THE NAME YOU SPECIFIED}/SC_Board_Background.png
EXAMPLE: /media/ui/boards/MyCustomName/SC_Board_Background.png
-- Texture resolution required: 890x620.
-- I recommend leaving the first and last 30 pixels transparent; they contain the board control panel.

For a dynamic texture, create a folder: /media/ui/boards/{NAME AS YOU SPECIFIED}/ads
Place textures in it with the following names SC_Board_Dynamic_{ID}.png
The numTexture parameter must be equal to the number of textures.
If you created SC_Board_Dynamic_1.png SC_Board_Dynamic_2.png SC_Board_Dynamic_3.png then numTexture should be 3