Bit more info re the conditions - semi shade, is it under trees? Near a hedge? is the soil regularly dry or quite moist?

Also,trees, shrubs, perennials...a mixture.. ?

Epimediums are interesting and not as popular as they should be, also any Corydalis varieties. There are many unusual bulbs like Uvularia (watch out for slug damage) or, if your soil is right, how about Meconopsis, the blue Himalayan poppy...now there's a challenging plant!!

Melitis melissophyllum (bastard balm) is a native plant for semi shade, dead easy to grow and doesn't take over the garden. If you go to my home page and click on the Garden tab, there will be a picture of it (probably on about page 4)

some of the more unusual aconitums eg ivorine, would fit the bill as would smilacena. Heleborus foetida 'Wester flisk' is a pretty leaf colour form. Species of Digitalis too.
Then there are lots of bulbs/corms too. erythroniums come in a range of more unusual colours too.
Dont forget ferns too. I have lots of semi shade plants too. by all means have a look on my plant profiles.