Change the wtfos images on your DJI Goggles
To change the splashscreen image, put an image named splashscreen.png in the root of the SD card.
To change the screensaver images, put images named screensaver01.png and screensaver02.png in the root of the SD card.
Try to use 16:9 images or be prepared for some stretched results!
Plug the SD card into the Goggles and power them on, it may take upto 30 seconds for the images to change the first time as the goggles need todo some processing on the images.