Simple one, use Gravatar instead of default image for your users if they haven't added a profile pic.
https://en.gravatar.com/site/implement/images/
related idea
APP-I-6440
users shouldn't have to make a Gravatar account just to add a photo, though.
related idea
APP-I-6440
users shouldn't have to make a Gravatar account just to add a photo, though.