I agree with several suggestions here. I also wanted to say I agree with Cindy. It's really a difficult thing for many parents because they are watching someone they raised making drastic changes. My parents have pictures of me when I was young in dresses and braids and pigtails. My mother is very supportive but those pictures helped her. She cried a lot when I told her I was transitioning and it was harder because I hadn't seen her in years and I was living overseas. She needed something to hold on to. I could never ask her to forget what I was like when I was younger. Those are precious memories for her. My Dad and I have a rocky relationship and honestly I don't care what he does one way or the other. It's likely I'll never see him again and if he wants to bandy about saying he has a daughter, I don't really care.
Maybe tell your parents what picture bothers you the most and ask them to put it in their bedroom. Start with one photo at time so that it's less of a blow to them and it still gives them time to adjust. It also will help them feel like they have some level of familiarity instead of just asking them to get rid of all of them at once. Their bedroom is their space, so I wouldn't tell them to take those pictures down. No one should be going into their room except them anyway, without an invitation.
Edit: I just thought of something else. My partner and I went to Las Vegas and we had a picture taken at an event that we both liked so we purchased. It was about two years before I began transition, and it's the photo that my partner kept in his office for years, even after I started transition. He would have taken it down if I had asked him to, but it was a fun memory for both of us and I don't really mind. It's a little odd to see what I looked like, but now it's just a curiosity in the house. We also still have our prom picture somewhere in the boxes of stuff we haven't sorted through since moving back to America.
The picture from Las Vegas is in a folder that can be opened or closed. If your parents aren't comfortable with moving a specific picture, you may be able to suggest a folding frame that can be closed as the first step and see how that works.
Sent from my SM-G920I using Tapatalk