You could make a heather bed from your raised area. There are delightful shades of pink, purple and white weather heather. If you put in enough plants they will soon spread out and cover the whole area of bare soil and give you a wonderful spread of colour in early spring. The good thing is that they can more or less be left to themselves without maintenance and the only work you will have to do will be to trim back any plants back after flowering that are spilling over the edges of the bed onto the lawn.
Yes, you can buy special black soil covering from garden centres but it's not plastic. It's a porous material which will let the rain soak through and is often used under forest bark. You could, of course, put down the black lining to prevent weeds growing, cover it with forest bark chippings and perhaps put a couple of containers on it which you could fill with bedding plants in the summer which wouldn't involve too much work.