Modify group name
If you are a group owner, you can choose to modify the group name, and then you can update the group members' avatars.
Reattach group members
If there are fewer group members, you can move the group members out of the group chat and then bring them in, and the avatar will be updated.
Play the trumpet and join a group.
You can also pull a trumpet into the group, then update the group avatar, and then change the trumpet to quit the group.
How to change the WeChat avatar: Open WeChat, click the "I" option in the lower right corner, then click the personal avatar, enter personal information, click the avatar, select a favorite avatar in the photo album, click the "OK" button, and wait for the system to upload it automatically.
Generally, the avatar will not be updated immediately in WeChat group chat. If you change your avatar, you may still see the original avatar, and you need to click on the avatar to refresh it into a new avatar.
This answer is applicable to WeChat version 8.0.7.