How do you fill empty hallways and walls?

Also a big fan of using surfaces with decorations in hallways. The narrow tables are good for exactly this. I like to sometimes use "end" versions of counters (the ones you have access to with auto turned off) that have little shelves with stuff on them under the cabinets. If you put the right clutter on, based on a nearby room, it can look like it has real purpose.

Oh, and a combination of house plants and one of those storage chests can be good too.