Hello La,

See if the following can help you.

/**
 * Set different default background images based on user roles
 *
 * @param array $settings
 *
 * @return array
 */
function buddydev_set_custom_default_profile_cover( $settings = array() ) {
	$displayed_user_id = bp_displayed_user_id();

	if ( user_can( $displayed_user_id, 'list_users' ) ) {
		// Users with administrator role.
		$settings['default_cover'] = 'http://example.com/cover-admin.jpg';
	} elseif ( user_can( $displayed_user_id, 'moderate_comments' ) ) { //editor
		// Users with editor role.
		$settings['default_cover'] = 'http://example.com/cover-editor.jpg';
	} elseif ( user_can( $displayed_user_id, 'edit_published_posts' ) ) { //author
		// Users with author role.
		$settings['default_cover'] = 'http://example.com/cover-author.jpg';
	} elseif ( user_can( $displayed_user_id, 'edit_posts' ) ) {
		// Users with contributor role.
		$settings['default_cover'] = 'http://example.com/cover-contributor.jpg';
	} else {
		// Users with subscriber role.
		$settings['default_cover'] = 'http://example.com/cover.jpg';
	}

	return $settings;
}
add_filter( 'bp_before_members_cover_image_settings_parse_args', 'buddydev_set_custom_default_profile_cover', 40 );

Regards
Ravi