It is possible to get some info from someone's license plate, but there is often so much more info embedded in the picture itself. Most cell phones and many modern cameras will geotag photos with precise coordinates of where the picture was taken. If you have image editing software, it should be able to display the 'EXIF' info which contains metadata about the photo - camera type and settings, time, location, photographer's ssn and bank account info...
Will I cover up the tag when I'm selling a car? Sure, sometimes b'cuz Craigslist. In general with photos? Why bother.
