I'm going to hang the small puppy on the wall.
Is there a good reason to harm a puppy in that way?
Because it does not belong to its owner.
It is wrong to scare or hurt an animal by hanging it up on a wall. You should be more compassionate with animals or you should avoid being around them if you have an urge to hurt them.
It's ok, I'm taking care of it.
If you mean by hurting the animal, I think that you should reconsider. You should not hurt an innocent animal on purpose.