Your direction depends (I guess) on how much DIY effort you're willing to put in? For example, you can get 12v LED strips which are IP67 (waterproof inside a s

Your direction depends (I guess) on how much DIY effort you're willing to put in? For example, you can get 12v LED strips which are IP67 (waterproof inside a silicon tube) pretty easily [0] and which would probably give a much more impressive effect than a string of Christmas-style lights, due to having lots more LEDs to play with. However, you'd need to do the leg-work of also buying and programming a micro-controller (something like an Arduino, ESP32, or ESP8266 [1]) and figuring out how to power them from your car battery. You could probably house all of the electronics inside the car and just run wires out of the boot, relying on the existing boot seal to keep everything waterproof. [0] https://www.aliexpress.com/item/1005004289391906.html https://www.aliexpress.com/item/1005004289391906.html [1] https://www.aliexpress.com/item/1005005977505151.html https://www.aliexpress.com/item/1005005977505151.html