As you can see from the recipes above, stone statues and quartz statues are crafted like armor stands, but with stone or quartz blocks instead of sticks.
Statues act like armor stands with arms; however, they share the model of the player. Additionally, armor pieces and items put on the statues are given the textures of the quartz or stone.
Statues have two states: default and powered, the latter being when it is receiving a redstone signal. Normally, the unpowered state is the stance of the armor stand with its arms at its side, and the powered state is the stance is of the player running.
However, if certain items are equipped, the states are a bit different. If a bow is equipped, the unpowered state is with the bow at the statue's side, and the powered state is the statue pulling back the bow as if it were about to fire. With swords and axes, the unpowered state is holding the weapon at its side, and the powered state is holding the weapon up.
When statues change states while holding a weapon, players and mobs standing right next to them take 1 heart of damage. This could be used for fun traps and could simplify mob grinders.
Renaming a statue in an anvil to the name of a player gives the statue a light grayscale overlay of that player's skin. Once placed in the world, you can right-click on the statue with any dye to make it exactly like the player's skin without the grayscale filter.
Overall, stone and marble statues would be great additions for decoration, as they would act as a new way to display items. Perhaps they could be used in some structures, such as the Woodland Mansion.