This mod allows a custom background in raid, it should be used as a base for any menu background mod(meaning no name changing of the mod!)
believe it or not but in Raid WW2 you can install blt mods in mod overrides and this mod you have to install in mod overrides.

To make a mod that uses this as a base just edit the texture at custom_background/guis/textures make sure the background fits inside the blue area, I had to do this image size because of dds pretty much and then just make a zip of the mod, if you want to you can include the mod.txt and the script if not you can delete them and ask them to download this base first.