The tribal was not a huge new thing for a Maiden. Although they never did it in such a large chunk of one song. But if it was big surprise than it was about the only of the last few years.
Empire of The Clouds: Maiden doing a rock opera with a large piano intro.
Satellite 15: Long as hell intro filled with electronic effects in a futuristic ambiance.
Brighter Than A Thousand Suns: Never did I heard Maiden doing such intricate patterns when it comes to time signatures... plus the desolate eerie ambiance is quite unique.
Face In The Sand: Full orchestral epic with double kick all the way.
Blood Brothers: Celtic influenced theme with a waltz time signature.
... and bear in mind that Maiden is one of the bands that sticks more to their formula. Yet even them manage to pour some stuff they never tried before in every single album.
Some of the bands/ artists I mentioned have careers nearly 30 years long (some already been 40 years in the business) and you still can't figure out where they're going to pull out next: Devin Townsend, Ihsahn, Opeth, Enslaved, Sepultura, Ulver, The Cure, Peter Murphy or Depeche Mode (and how could I forget acts like Killing Joke, Pyogenesis, Cynic, Faith No More, Witt and Nine Inch Nails? To this day you never know what to expect from each release).
Don´t forget AC/DC and Motörhead.
Regarding bands that hardly change there are many more... like The Ramones, ZZ Top, etc. But the point is not proving that there are bands that stick religiously to a formula. It's precisely the opposite: debunking the myth that if you're x years deep in youre career you simply aren't able to bring something new to the table. And I think I pointed some good examples.