I have reverse lights on the trailer but they only help the DW not trip over anything. They don't help me at all because I can't see behind the trailer and also can't see the DW because she is usually standing behind the trailer! :B
One big issue I have is reflection off the front of the trailer. The glare on the front of the trailer makes everything beyond that point look like a black wall. To eliminate the reflecting glare I tape shop rags over the TV tail, brake, and reverse lights.
Use a yellow extension cord along the path you want the trailer tires to travel. A yellow cord appears white in the dark. You could alternatively use a white rope.
I added a porch light to the street side of the trailer. Switching on the curb side and street side porch lights helps me see beside the trailer while backing.