How about a ground cover of a prostrate variety of blue Colorado spruce ?
See photo at link below.
I bought five small ones by mail order from Whistling Gardens in Ontario this spring (its fairly rare in cultivation -- not many nurseries carry it....).

Here is a link that might be useful: Picea pungens 'Gotelli Prostrate'

I love this look and it would work. I'll check with a local garden centre to see if they could order it in for me.
Thanks
RRR

How about Sea Buckthorn. It's extremely hardy and can even stand salt.

I have sedum for ground cover here (in New Brunswick). We are along a river, not the ocean, but this stuff grows well almost anywhere! Also have flox and spurg which grow well for ground cover.

I have oak trees planted that do very well (but a bit messy with all the acorns). I would think just about any everygreen would do well.