You two accomplished a great deal together and the photo will be tangible proof for him of how much he helped you. As a professional, that will feel great for him. Also, I think that it's progress that you were able to connect to this T enough that you WANT to share with him that you can do this fun and exciting thing through the hard work you did WITH him.

Be aware, though, that he may not respond. I have sent three letter to my former T over the last 25 years or so since I stopped therapy with him. He responded to one of them, but not the others.