Perennial window box planting - please inspire me

[ComeIntoTheGardenMaud]

For reasons of stinginess environmental awareness, I am trying to make my window boxes less dependent on annuals. I have one quite successful one at the moment with heuchera and ivy, but am feeling uninspired about what to do with the others. One is in shade but the rest are in sun.

Please share your best ideas!

I have perennial pots outside that contain:

Ivy
Lillies
Primroses
Pinks
Panies
Small box/ Hebes

Ah yes, perhaps a small buxus as a centrepiece. The trouble with window boxes is that they can't take anything that needs to be planted deep - I love lilies but already have them in big pots.