I'd have to agree with A/B testing this one. It depends what your audience wants to see or what they expect out of your company.
For instance, at Autosend.io we tested a personal photo in the signatures of our blog posts with a personal email and we tested it in our feature box where users subscribe to our blog. Although human photos have high conversions on average, we found it depends what the users are doing if it actually does. It also depends on what picture you're using, the gender, etc. As you can see, this is why A/B testing is required.
We're also considering running a test like this for our personal welcome emails and some of the emails we've automated to go out when customers need help in our app.
Maybe on your registration page it doesn't even have to be your face. Try some of your top customers based on what kind of customer you're trying to attract. So, if you're trying to attract a small, solo-preneur...use an image of one, with their title, testimonial, and a very short description of their company.
Again, I think timing, your customer base, and your brand play a lot into the conversion rate of a personal photo.