What I love about Minecraft is searching for the rare things. I think in the next update rare items (mainly for display) can be located in the various locations. There would be three levels of treasure. For example in the jungle temple there would always be an easy loot found in a chest but then there could be lower % chance of finding a greater treasure. The rarest being a Golden head statue. Some treasures could be found resting in certain spots. In the Pyramid temple you might find a statue of Anubis - maybe it's buried.

Each treasure could also have a use as the pyramid treasure has the potential to summon a mummy. The golden statue could trigger a tribe mob that seeks out to kill you. And maybe if all the treasures are found some new item can be produced, or a portal to a new dimension. 

Also there could be certain treasures underground. When I find a diamond I Always smile, but what if some of the diamonds were the color red or black? Maybe a 1% chance, and that would allow for armor to be that color in Diamond form.  Or maybe in the lush jungle there is a rare flower that spawns 5% of the time that produces fruit that gives temporary boost.  Maybe in the jungle you can find a special kind of mud that heals.  

Also fishing would have a chance to find certain treasures too, I think fishing overall should add more items to be found.

Finding these rare treasures would make me want to explore more and create a trophy room to display what I have found.