Wechat background can be set. Maybe your method is wrong, or you can't find it. Let me show you how to operate it:

Version: 8.0.37

1. Open WeChat, click Discover, and then click Friends Circle.

2. After entering, tap the background picture.

3. Click to change the cover page

4. Choose the form you want to change (I take photo album as an example).

Select photos

6. Click OK

So it doesn't matter