I was just there this past week and it had the Night Before Christmas overlay, so I couldn’t see the actual portraits. However, the side of the elevator you want to go to depends on which elevator you get into:
When you enter the mansion (black arrow), you will either be directed to the elevator on the right (blue arrow) or to the left (red arrow). If you go to the left elevator, you will need to enter the elevator and then shuffle over to the wall on the right. If you go the elevator on the right, you want to shuffle over to the wall on your left after entering.
My super secret trick, is if you look close enough, you can see the “false wall” when you go in too, just in case you get turned around or distracted as you’re ushered in.