I suspect you'll need more soil. I also wonder if the hydrangea might have gotten too much sun. If more soil isn't an option you could do a succulent garden. Hens and Chicks, Prickly Pear(turns grayish purple and lays on the ground after the first frost), any number of Sedums and Portulaca for bright color. These need very little soil and no fussing over at all. But you have to have good drainage. You could add rocks, which never die back in the winter! I think there is a rock gardening forum around here somewhere that could give you some good ideas.

Another nice shrub for shade/part sun that has good winter interest and a striking burst of yellow in the spring is Kerria Japonica Grandiflora. It doesn't need pruning because of it's lovely fountain shape. The canes are beautiful bright green all winter long. It spreads by runners and can get quite wide and tall. You could underplant it with a groundcover like Plumbago, which has bright blue tiny flowers in late summer and foliage that turns red, orange and rust in the fall (all the while covered with those cobalt blue flowers), before it dies back. Warning, this groundcover is a spreader that you might not want in your other beds.

Good luck.