Originally Posted by Sohkraites
...Just wasn't to make sure we have enough light!
In the end that really depends on how you
plan to use the trailer. For us it's more a hard-sided tent: a place to sleep at night, nap during the day, store and change clothes. We cook and eat outside, and spend most of the day doing "outside" stuff. Evenings are for campfires, right up to bedtime. So for us the minimal factory lighting is perfectly adequate. But if you will be cooking inside, you'll probably want more lighting in the kitchen work area. If you plan to stay up reading inside the trailer, you'll want to plan some adjustable high-output lights. If you will be touring for extended periods, or using the trailer much in inclement weather, you'll want more and flexible lighting.
Best to put in all the wiring now, while the walls are bare, even if you don't immediately plan to install a fixture. It's harder to add wires later, after the walls are covered.
One more recommendation (which I don't think has been mentioned yet; forgive me if I missed it)… you might consider adding a second set of taillights above the belly band and converting both sets to LEDs. Now's the time to do it because the wires run inside. The stock taillights are weak, and can be obscured if you put anything on the back of the trailer or if a tall vehicle is following too closely. There have been several recent reports of trailers being rear-ended, and the results aren't pretty!