MTG: How to improve my mono white angel deck?

You don't really need the Elspeth if your walls are doing their jobs. I think twenty-four lands are too many, but that's tempered by your experience playing the deck. Luminarch is a seriously powerful card that really makes the other angels unnecessary in my opinion. Maybe take out the smaller angels and replace them with walls? One word on the Crusade though. Yes, two mana for +1/+1 to your creatures is great, but remember it gives the boost to ALL white creatures. You may not play many other white decks, but I would spend one more mana to use Glorious Anthem. It takes one colorless mana more to make all YOUR creatures get +1/+1. One more mana seems like a good trade-off to keep your opponent from getting that +1/+1.