Armor Stands show in the Creative inventory as a Decorative block with the name minecraft:armor_stand
http://puu.sh/cs2zp/3824ed1831.png

However if you try to use /setblock command with them you get an error that
"There is no such item with name minecraft:armor_stand"

The summon command does work, but that is inconsistent with the rest of the items in the list.