I figured I'd vary it up a little and do something different on each light. For the first one, I tied a 5 lead 4 bight Turk's head knot(the same to start a Gaucho) and raised that to a 7 lead 6 bight knot, doubled it, then did some spiral hitching, and finished with another 7 L 6 B knot.
The raised TH knots tend to get a bit skewed on me(tying on a mandrel with pins could help with that) and this time was no exception. My blood pressure was up and I got impatient while tying, and would normally untie and start over, but I decided to leave it be and will try to take my time with the others.
I guesstimated on the length of cord I'd need to cover the exposed shaft that will be sticking out of the ground. Tying directly onto the light, I started with a single 20 foot strand of 2mm cord, and when done, ended up using 18 feet.
There are many options when choosing the outdoor path lights, different finishes, shapes, and output, and I'm sure some are more durable and weather resistant than others, but I went with the $0.97 models from wallyworld and will see how they hold up over time.
I doubt most of the folks that walk up to our front door, ignoring the 'NO SOLICITING' sign, will take any notice of the knot work on the lights.
Other potential places for decorative knots outside the home could be fence/lamp/mailbox posts, porch columns, lawn furniture, playground equipment, swing sets, tables/chairs, etc., and try using glow-in-the-dark paracord for a neat cord option.
Another one shown with a long 4 bight Turk's head knot.
The last two were done with spaced out Spanish ring knots and 5 lead 4 bight doubled Turk's head knots.