There are some Pokestops / Gyms in my local area where they building, playground, etc has been completely remodeled and the old photos show from when they were still decrepit. I always feel embarrassed exchanging gifts from some of them on routes.
It would be good to somehow mark a photo as outdated.
I agree! In the meanwhile, if you are level 38 or higher, you can submit new photos. Then you can thumbs up the photos in PoGo to indicate you like this photo. If it gets more thumbs up than any other photo, it will be come the new disc photo.
You can use help chat Niantic Wayfarer to request that photos be removed. But there will need to be a new photo in place for them to do that. And they have to be convinced that it needs to be removed.