If you choose wallpaper with lots of pattern, you will have very little need for pictures or artwork. When choosing wallpaper, don’t assume that a small foyer should be papered with an equally small printed design. Some of the prettiest foyers I’ve been in, were small ones, where the paper chosen was large scale and very bold. The effect was wonderful! The entry is the perfect spot for tromp l’oeil. Possibly a mural of a Grecian urn or a large topiary.
In a small foyer maximize the light and make a tight area feel less cramped with a floor to ceiling mirror. Your foyer may be a tiny space with only a coat closet and no place to hang a mirror. So why not mirror the closet door! This will make your space appear larger. Depending on how your closet door is positioned, it may double a gorgeous view of the outdoors.