We usually just leave them as is, we have however used them when we were short of towels.
I asked a friend at the Polynesian the policy about taking them and at that particular resort they are considered room decoration to be enjoyed during the stay and are not to be removed anymore than anything else in the room.
In fact when I asked, she was amazed anyone would even think they could take them, and I told her I think some maids had said to. Her response, Well I guess the maids that do that can pay to replace them. As they are part of the inventory. JFI
So anyone considering "taking" them you might want to ask management their policy.