Allow us to add background on the calls

After a recent update, you see a background behind the avatar when on a group or private call.

This can look way better by:

• Allowing us to add a background of choice so it doesn't have only one color as a background.
• If it's impossible for you to make us choose a background of choice, at least make a selection of backgrounds available for us to choose.

Thanks to a friend that gave me this idea.