Several of my friends as well as a few of my neighbors do not allow anyone outside the immediate family to enter their bedroom even when it is empty. (Occasionally, when visiting a friend who recently bought or updated their home, I am curious to see how they decorated their bedroom - sometimes it gives me ideas on how to do mine.)
All these people said that the bedroom is halichally considered a private place and one is forbidden to invade another person's private, personal space.
I can understand the concept of the privacy, overall. But I'm curious if there is any halacha per se that would prohibit seeing an unoccupied bedroom.
Note: This question focuses on the type of marriage that would allow or prohibit this action. My question assumes only a valid Jewish marriage, and asks specifically about an unoccupied bedroom.
(Other than halacha, I'm not sure how to tag this question; please assist / edit)