BuddyPress.org

Try this.
Add code to functions.php or use Code Snippets plugin (easier)

function rename_rtmedia_profile_tab() {

buddypress()->members->nav->edit_nav( array( 'name' => __( 'Photos', 'textdomain' ) ), 'media' );

}
add_action( 'bp_actions', 'rename_rtmedia_profile_tab' );