I tend to have trouble with visualizations most of the time, so the safe place concept is hard for me. Lately is been with a t I trust, in her office. But that's an actual physical place where I feel safe, not something I can much use when not in session.
One time I was able to picture t in my room with me, that helped me sleep that one night, but it was Also kinda weird (though we talked about it after and she was ok with it). Sometimes I can feel safer with my critters around. Other times is out in nature, but it's rarely an imagery thing for me because I just can't summon the safe feeling with the images...