Lirope or Mondo grass would work really well for a narrow space. Other plants that come to mind are ferns or cast irons plants.

I have spider/airplane plants in a shady area. I put them there to keep the dirt from washing off. They die back in the winter here and come back in the spring.

caladium

Cast iron plant is a traditional southern shade plant and as the name suggests very hard to kill. I find its a slow spreader so plant enough to fill in the area you want or looks nice grouped with flowering annuals between.