Unfortunately once the initial wallpaper is set, we can’t change the image anymore. Even not by setting different initial wallpapers for each script tab. Because the last applied wallpaper will be the one and only initial wallpaper for the whole instrument. But we can either offset the initial wallpaper that means moving it via set_skin_offset() or we can use a label element to set up multiple backgrounds. Even dynamically like switching them on a button event. The set_skin_offset method is explained in this article
The instruments background image is called “wallpaper”. Its’ the basic background texture where all UI elements (knobs, buttons etc) get layered on top. Just to give you an example: we could take our default graphic software and design a realistic synth surface wallpaper (png file) containing “sockets” for some knobs and buttons with detailed shadows, light reflections etc. After on we can create the individual knobs & buttons and place them exactly inside the designated sockets and areas by layering them on top of our background wallpaper.
Like in other programming languages in KSP there are variables, arrays and constants. These can only be declared inside the on init callback but can be used throughout the whole script then. Read more »