Being able to see in the dark is really nice; and when all you need is a small amount of light to find your way around your camper shell, recycling ornamental/holiday LED lights might just suit your needs!
Step 1: Supplies
Solar-Powered ornamental lights (usually found at the Holiday or Garden section of your nearest Dept. store), wire clamps, zip ties.
Step 2: Easy!
1) Use the existing window screws to attach your wire holders in place.
2) Zip ties hold your LEDs onto the wire holders; the perimeter of your camper windows act like a readily available track for your (ambient) lighting system.
3) I used a small magnetic basket to hold the solar panel of my LEDs. This model recharges its batteries in the sun, and goes on automatically in the dark (unless I turn the unit OFF).