OK i see your issue, you have the file type in the game name, that should not be there. They are .z64.zip so Launchbox thinks that .zip is the file type so is keeping the .z64 in the file name, hence not matching the correct name. I have no idea where you got those roms, but i would suggest unzipping them all and re-importing. I think you will find you get art for everything that way.
That is a really strange way of naming the roms that you have, i dont know who's idea that was, but frontend software of any type will struggle badly with that naming scheme.