I think that the author of Element TD has just edited the normal armor types, this can be done in the World Editor.
Go to Advanced -> Gameplay Constants, here you can change how different armor types works (this is edited in the Combat section there).
In Advanced -> Game Interface, you can edit the icons, names and tooltips of the armor types (see the Icon and Text Message sections, it is there somewhere).
About the maps that you cannot open, the author has "protected" them. This mean that he/she has removed some files from the map archive that are only used by the World Editor and not by the game, either manually or with a 3rd party program such as Vexorian's
Wc3 Map Optimizer. This means that the editor can not open the map, but the game can.
People usually do this to prevent people from editing their maps, so they can't make any harm to them, such as replacing the author's name with their own. Some people just do this to make the map smaller because of the useless files that are removed, so it becomes easier to distribute it over battle.net or similiar.
There are ways to "unprotect" maps, but as map authors usually have good reasons to protect their maps. So we won't help anybody with unprotecting maps, but you can always describe what you want to do, and ask about how to in the forums or if possible contact the map author.
