There is Hedera helix in your bed (ivy), which will make adding plants very difficult. The soil will be full of ivy roots which are hard to get rid of; these roots will also be preventing the soil from suffering erosion by falling off or being washed down the slope of the bed. Even if you clear an area for replanting, the ivy roots will very soon take it back over, and there's the added problem of how to prevent soil erosion in the meantime. I imagine the ivy was planted to stabilise the area because of the steep gradient - if you try removing all the ivy, intending to replant, there is a real risk of serious erosion. If you want to clear and replant, I'd recommend you seek a suitably qualified landscape architect or garden designer to carry out the works.