Hall of Mirrors copies the printed values of the target creature. It won’t copy any counters or stickers on that creature or any effects that have changed its power, toughness, types, color, and so on, and a creature becoming a copy doesn’t remove any such counters or effects that are already applying to it. Notably, Hall of Mirrors won’t copy any type-changing effects that are currently making the target a creature. For example, if you choose a land that’s become a creature, all your other creatures will become noncreature lands until end of turn.