hello Sarah, thank you for this post. unfortunately i have not been successful at adding a custom avatar to our BP site. we are using BP version 1.9.1. i added

define ( 'BP_AVATAR_DEFAULT', 'http://www.penintime.com/wp-content/uploads/2013/03/avatar-1.png' );

to the bp-custom.php file and uploaded to /wp-content/plugins/ folder. can you please tell me why this is not working?

thanks so much.