Last week I ordered some LEDs from V-LEDS.com and they finally came in. I bought a pair of white LED license plate bulbs and a pair of 6000k white (no 5k available for this particular model

) back up lights. I removed the entire trunk liner and when I saw where the license plate bulbs were mounted, I thought "you've gotta be kidding me".
The bulbs were mounted at the most awkward angle you could imagine, and just trying to get your hand into the area where they're mounted is challenging enough. Twisting the bulb socket took some extra strength because that area has never been touched before. Toyota sourced some damn good bulbs, because after 12 years, the original incandescent bulbs still worked just fine. I finally got the bulbs out, swapped the LEDs in, and they worked.
The backup lights were much easier to deal with. No awkward angles to stick your hand into, and it was just a simple twist, pull, replace. I'll post some night pics when I get time.
Here are the LEDs I used:
License plate:
http://www.v-leds.com/Exterior-LED/C...-p6985865.html
Backup lights:
http://www.v-leds.com/Exterior-LED/P...-p7526829.html
The backup lights were expensive as hell, but I decided to give them a try. They are definitely much brighter than stock, and are somewhat blinding when you're standing behind the car at night, but the only problem is that the Avalon reflectors don't really reflect down towards the ground that well. Instead they reflect the light straight back. Either way, they made backing out at night while having 15% window tint a little easier.