Can the avatar of the elink assistant in the live streaming room be changed?

It can be replaced.

You can make unified settings for all live stream announcements, replace the assistant avatar, and change the live stream announcements in [Live Streaming > General Settings > Live Stream Announcements]. This setting will take effect for all live streams that have not had their announcements set individually (there may be a certain delay before the modified announcements take effect).

You can also set the announcement for a single live stream in [Live Stream Details - Live Stream Decoration - Live Stream Information - Live Stream Announcement], which will only take effect for this particular live stream.