The aluminum insulation tape and white ceiling help reflect light
When I built out the van, I installed LED strip lights. There are different types out there, but I used some flexible, self-adhesive ones that are marketed to people who want to jazz up their cars. I got them at Walmart and they're wired into my house battery system.
The tricky part was the wiring connections. The wires are so thin and my fingers are so thick. All I could do was twist the wires together and cover them with tape. I suppose some people would solder the connections, but my kludgy technique has worked fine. Also, LEDs are finicky about polarity. Positive to positive, ground to ground, or they don't work. I had the wire from the battery already connected so I could see the LEDs come on before I twisted the connections together.
Sometimes I don't want to light up the whole van or get up to reach the switch for the LEDs. And even though LEDs use very little power, sometimes I want to conserve my house batteries. So I got some touch lights powered by their own rechargeable AA batteries.
Here's a shot with all six touch lights turned on. To get a comparison of light output, the photo was done with the same manual exposure settings as the one of the LEDs.