There’s a “test” feature that Google is currently running in AdWords which automatically shows text ads in your display campaigns as image ads. I recently encountered this while on a webpage where I saw a really ugly image ad and noticed that it was for one of our clients. After looking through their account, we weren’t running any ads that looked like the one I saw online. So I reached out to Google’s Customer support team and was directed to this post in their help center about these Automatic Image Extensions.