You could re-create planting beds on either side of your walkway towards the top of the slope. They may be straight or even curvilinear. I would make them fairly long and have them tie into the walk/steps.
Consider some evergreen shrubs as a background for perennials to provide color throughout the season. You might use Boxwood, Japanese Holly, or Blue Holly. There are lots of perennials you could choose from. Just make sure they take a lot of sun. I would plant them in groups of 3 to 7 and alternate the flower colors, times of bloom, heights and textures.
You can get lots of information on perennials here:
Perennial Flowers.
I have also written an ebook on Evergreen Shrubs that you would find helpful:
Evergreen Shrubs
If you have any further questions, just post them here under Comments. I hope this was helpful.
