Something to plant alongside Cotoneaster Dammeri

I have this bank at the side of my garden in which I planted Cotoneaster Dammeri last spring. They are growing well but its going to a while before they cover this unsightly bank of poor stony soil. Can I have some recommendations of which I can plant alongside these to add a bit more interest and cover the ground a bit quicker?

 

If it’s sunny, how about hardy osteospermums.
Did a similar thing once to great effect. Cannington Roy (pink) and Eklonis (white) are both vigorous spreaders and great on the eye on a bank of poor soil

 

Perhaps some ground covering plants like Aubrieta and Campanula. They are easily removed as the other plants spread.