Find a focal point in room..maybe in center of room above a couch
Cheap and easy to swap out pictures: Put up a nice string/rope... use clothespins to clip picture to it!
You could do a gallery wall in a hallway: https://www.hometalk.com/search/posts?filter=gallery%20wall
I'm always a fan of picture ledges. You can mix it up without having to put tons of nails in your walls. https://www.youtube.com/watch?v=nbrSh-WHnxA