Background (GUI item property)
From modwiki
Sets the background of an item. This can be an image in .TGA format (a reference to the filename, without extension, with the path relative do the game installation directory) or a reference to a material on a material list (use the shader path/name as defined in the .MTR file).
Syntax
background material
Default value
""
Example(s)
background "gui/assets/scanlines"

