Powering LEDs from vanity lights

Er, if I understand correctly, you want to have some flat panels mounted around the car, each panel has some kind of printing on it and is lit evenly from behind? If this is the case I think you would do better to get some electroluminescent panels and have them printed with your design. You would always have the same color in the same spot though. There is probably a setup fee for the silk screening, you might go at this as a group buy, bring in some fellow fanciers, maybe push the unit price down a little.

If you went LED you'd either have to put them behind the panel, which makes it thicker and gives you bright and dim spots, or you'd have to experiment with getting a plexiglass panel and edge lighting it. This is more involved but would allow you to change colors. Both are dimmable and might be able to dim with the dash lights.

It is easy to run LEDs or EL off 12 volt DC, but if these are permanent I think you'd want them hard wired, not monopolizing the lighter outlets.

 

This guy:

12" x 7" Electroluminescent EL backlight glow panel - eBay (item 200196249223 end time May-28-08 11:42:50 PDT)

looks like he might be able to do the job. He'd probably want you to supply the image. Haven't dealt with him myself. Any EL item does need a little inverter to get AC out of your cars DC power supply. All EL items are internally AC. You might be able to pop out the light fixture and use that space for the inverters.