As it must be acid soil, how about heathers? White ones would look wonderful.

Ajuga reptans would do well as ground cover - its evergreen and creeping, comes in various variegated colours - Rose Glow, Burgundy Glow, variegata, etc. has short blue spikes of flowers late spring. Also Campanula muralis, again evergreen, purple flowers around June. Both these do well in shadier spots, as does Tolmeia - often found in the houseplant section, but gives a good, hardy light green cover outside. Heucheras are worth a look too - leaves from lime green, green through to pale orange to purple red.