Latest: I parked outside town (crowds, summer) and trudged to the Ayuntamiento, where a nice man told me that I don't need to be registered with the Padrón in order to get a NIE and that I won't need photos, either, just my passport and the NIE form. He said that they won't register me anyway until I know where I'll be living permanently and that campsites pay separately, so there'd be no need for the campers to be registered (as someone has said in this thread.)