I see that you're unable to change the wallpaper being used on your iPhone. I'm happy to help.
Change your iPhone wallpaper -- Follow the steps in this article.
If you're still having a problem changing the wallpaper on your iPhone, please answer the following questions:
- Which iOS is your iPhone currently on? Find the software version on your iPhone, iPad, or iPod
- Are you trying to switch to an Apple image or using a photo from your iPhone?
- Are you receiving any message(s) when you try to change the wallpaper?
Let me know how that goes.