As my trees get a little bigger, I'll have more room for shade plants. I really like ferns, so I'll be planting more of those...
Cinnamon Fern
Some of my shady plants
Male fern?
Ligularia. Nice foliage.
Big blue tinted hosta
Lime green color hosta. I love this color.
Pulmonaria
You might also want to try Davallia trichomanoides, the Squirrel's Foot Fern. It's a really lovely fern with reddish brown new growth that contrasts beautifully with the older green fronds. I'm really impressed with it.