The standard maps are located in data/gamedata_x1.drs . You can open and edit with any text editor, but if you do that it's like a patch or a mod, you can only play with other players having the exactly same gamedata_x1.drs . You can try adding a new map there and it might even work, but I never tried that.
Also I think you cannot change the map names in there since the map names are depending on the AoC language. You can take a look in the language_x.dll files, but since these files are in a binary format, changing them with a editor might break them (make save copies!).
You probably cant do that since they wouldnt be standard maps anymore... There is a reason there is a "custom" map section, for you know... custom maps.
Please leave alone the standard map section, i got enough **** like “----- arabia“ or “!!!!!GA200sheep“ in my custom already
don't spam maps in the standard folder :D