http://webdeveloperswall.com/buddypress/wordpress-social-login-facebook-profile-picture

wordpress-social-login-facebook-profile-picture

<?php 
add_filter( 'bp_core_fetch_avatar', 'revert_to_default_wp_avatar', 80, 3 );//late load
function revert_to_default_wp_avatar( $img, $params, $item_id ){
	//we are concerned only with users
	if( $params['object']!='user' )
		return $img;

	//check if user has uploaded an avatar
	//if not then revert back to wordpress core get_avatar method
	//remove the filter first, or else it will go in infinite loop
	remove_filter( 'bp_core_fetch_avatar', 'revert_to_default_wp_avatar', 80, 3 );

	if( !emi_user_has_avatar( $item_id ) ){
		$width = $params['width'];
		// Set image width
		if ( false !== $width ) {
			$img_width = $width;
		} elseif ( 'thumb' == $width ) {
			$img_width = bp_core_avatar_thumb_width();
		} else {
			$img_width = bp_core_avatar_full_width();
		}
		$img = get_avatar( $item_id, $img_width );
	}

	//add the filter back again
	add_filter( 'bp_core_fetch_avatar', 'revert_to_default_wp_avatar', 80, 3 );
	return $img;
}

/**
* Check if the given user has an uploaded avatar
* @return boolean
*/
function emi_user_has_avatar( $user_id=false ) {
	if( !$user_id ){
		$user_id = bp_loggedin_user_id();
	}
	
	if ( bp_core_fetch_avatar( array( 'item_id' => $user_id, 'no_grav' => true,'html'=> false, 'type' => 'full' ) ) != bp_core_avatar_default( 'local' ) )
		return true;
	return false;
}
?>