Interesting time for you to post this as I just finished researching my T also.. LOL
It did feel a slight bit odd, but not so much. We live in a new age where you use technology to learn about people. IMHO, it is just what it is. I don't find anything you did to truly be out of line, but I could be wrong. I would have done the same thing.
The therapist is trained to be almost unreadable in sessions and keep the focus off of themselves. It is extremely difficult to have a relationship with ANYONE, even a therapeutic one with someone you feel you know nothing about. I there are some reasons for that, but I don't feel that internet research (even looking at the house pics) is crossing a boundary in my mind. Seeing the pics of someone online, their home (if easily viewable to public and you are not out paying someone to stalk or something...LOL) just gives you a bit of a better connection to that person.
This is all my thoughts and I hope I am not sending the wrong message. I don't even honestly feel the need to tell my T tomorrow that I just finished googling him. I don't feel like I am hiding anything creepy, I think it is just an expectation in today's day and time really.