There are a few situations where the aerial images on the GPS screen wont be displayed.
For a white aerial view, the images may not have been downloaded. While in your round press menu > Reload GPS Imagery. You will need to have a strong internet connection in order to download the imagery. Your course must also have been mapped with Google imagery in order to be displayed.
If the GPS screen is only showing the GPS list view, a setting might need to be updated. While in the round press menu > Make sure GPS View is turned on.
If you have any further issues with the images contact support here.