I don’t know if anyone else finds the interior (rear cabin) light a bit dim, but the one in my 2003 RAV4 3-door is. Replacing the tungsten “festoon” bulb with an LED type would have brightened things up a bit, but the location of the light source leaves a few dark corners in my opinion, so I extended the illumination by adding a strip of 15 LEDs taken from a broken kitchen cupboard downlighter which uses 12V DC.
I used the existing holes in the original interior light holder to take my power feed from, so that I could return to the original setup if I ever wanted to. The long, lightweight flexible lighting strip attached to the roof lining with two 6mm “flat” cable clips, taking out the integral nails and replacing them with screws.
Safety note: I removed the battery negative connector before starting any of the investigative work. With the circuit powered, I used a multimeter to identify the positive and negative terminals in the original bulb holder, marking my additional wires with a red and a black Sharpie pen so that the LEDs were wired correctly, because the strip connector had two plain white wires, but the printed circuit board was marked with + and - signs).
Photos show the results of this DIY project. The picture of the original light fitting was taken at an intermediate testing stage.