How can I get my full screen caller pictures on my XS Max?? I’ve had it with every phone until now.

Try the following steps.

http://www.itchban.com/blog/2015/1/23/fullscreen-caller-id-on-iphone

What worked for me was to Edit the Contact photo directly in the contacts app. This assumes that you already have a photo associated with the contact in the app.

Select your contact in the contacts app, tap on Edit. Tap on Edit under the contact photo. Make a slight adjustment to the photo. You can move it slightly, enlarge it a little, reduce it a little, any minor edit at all should work. Tap on Done. When you receive a call from that person, you should get a full screen photo now.