A custom default avatar is something that can greatly increase the visual appeal of your BuddyPress site. I don’t have to sell you on this. When I see those ugly monster avatars littering a BuddyPress site, my first instinct is to leave the page. Aesthetics play a huge role in your site’s ability to keep users around long enough to find out what you’re about. The default avatar is also another opportunity to keep your brand consistent throughout the site.
Banish the Mystery Man, Ugly Monsters, and Trippy Patterns
How to Change the Default Avatar for Members in BuddyPress