This isn't an your business and preoccupying... Should be pretty obvious of why those other downloads categories haven't been added...
We still haven't started with put the main downloads for MM1, which are vehicles, tracks and mods. There's no need to add these others too, for now. The brands subdivisions are required when the amount of vehicles will increase, exceeding at least 2 pages.
Then, those other particular categories haven't a great amount of releases concerning MM1: surely exists a complete savegame; the music tracks can be easily get from the game disc in MP3 file format, but there's no release of them actually; various tools exist.