Here's another idea for those large foyer walls that you don't know what to do with. This is my friend's foyer. She was frustrated with this wall, so I gave her this idea and she put it into action.
She:
1. Painted a large square on the wall.
2. Purchased stock plastic molding at the home improvement store.
3. Painted the molding and antiqued it.
4. Attached the molding directly to the wall with nails.
5. In this case she had a decorative painter come in and antique the painted square and add the decorative scrolling.
6. Hung the picture in the center.
Didn't she do a great job? This is an idea that could be interpreted in many different ways, so hopefully it will be helpful to someone.
As always, let me know what you think.