Another one to consider (in addition to general purpose power and telephone),
is electrical fittings specific to lighting
devices. In my mind, I am thinking a two
pin polarised connector (one pin bigger than
the other), shrouded to protect the pins.
The wall receptacle would have the likes of
a 3A fuse or CB, recessed, the females on
lighting extensions or lighting strings would be shrouded. Also available would be a device to fit into a GP power fitting, which
would have a fuse/CB and a switch.