I think that this may be perfect door for a dining room opening Sliding Barn Door Hardware craftsman entry
french pocket doors with transom window above
Frosted glass french doors as seperators for bedroom/dressing room.
Metricon Jasper - Theater door; another nice way of opening up the den
Make a pocket door like this and put photographs over glass panes for now when it's a bedroom then remove later.
interior french pocket doors | Features and Functions of Custom Interior Doors
Glass barn doors...LOVE them
Stained pocket doors
Office Reveal | Life On Virginia Street. Gorgeous office with a great source list! (Love the sliding French doors!)
@Kayley Miller this office door situation is fantastic (by @Melissa @ Veranda Interiors)