The most obvious place to decorate with erotica is in the bedroom. The bedroom is the last refuge for relaxation and romance for the vast majority of people. It should be a place that has an aura of sensuality and ease. Erotic art can provide that aura. The second is less obvious.
Bathrooms are one of the most neglected rooms in any house.
Which is a pity since it is a room which we are absolutely obligated to visit at least once a day. Many people report having some of their deepest and most profound insights whilst seated on this pedestal. I remember meeting one sophisticated German lady who was living in Australia. The effect was stunning.