It actually isn't in the settings, it's on the main screen. When I plug the phone in, the android auto lights up on the screen in the car, but the image button still stays dark. I've tried having gallery opened up when I plug the phone in, that doesn't work. I'll have to find a thumb drive and try it. Thx.
UPDATE:
Ok, so I plugged in the usb stick with some pics, and I was able to access them via the image button. But there's no way to set that picture as any kind of wallpaper. I could slideshow them with the usb stick in, but as soon as the stick is pulled, poof! Yeah, it's kind of neat to be able to see pics on the display, but isn't that A) Useless as tits on a bull, and B) counter productive for safety?