The difficulty with your relatives, and the commenters, is they don't understand PTSD or anxiety. PTSD and anxiety are the result of an entirely form of brain function than "normal memory." They don't understand that people can't "just get over" PTSD and anxiety. And they don't understand that certain memories will trigger the PTSD and anxiety, just like certain plants will trigger an allergy attack.

Until they understand that, there's very little you can do with this.

Whether the event warrants anxiety is not their concern, nor is it a useful discussion for anyone involved. Again, if you were allergic to some houseplant in their home, and they refused to remove it, you would be fully justified in saying you can't come over.

The only suggestions I have are...

1. Struggle not to encourage them to remove the pictures. Instead, struggle to educate them about PTSD and anxiety.

2. Continuing with the allergy analogy, there is no reason why they can't be invited to your home.

3. Many people have suggested your family is actually abusive. We don't have enough information here to know, but I do know people who enter into highly abusive relationships (such as your previous marriage) are often taught this need by their abusive families. Perhaps you should examine if this is the case. If it is, it may be best to remain distant from abusive relatives.