I can see the ember chest and earth chest but I can't see the halloween chest in there. I can also see: Treasure of Heroic Bounty Locked Gemstone Cache
There's 3 item chests. Ember Chest, Earth Chest, and Halloween Chest. The other 2 chest items are for crafting scrolls and gems for socketing I think. Here's where you can see what got in. http://tf2b.com/updates/d2t
I think as long as the item doesn't look out of place, it is fine. You can see many halloween themed sets that got accepted in the game. As for masks, there is this guide written by Vlad (or Vermillion Wlad) and this guide written by T_Vidotto. Check them out