I would put some climbers up the fence Clematis perhaps, certainly for this year, sweet peas are quick.
Pick the perennials you want to grow there and space out, then get a packet of those mixed annuals and sprinkle them in between for the first season, to get the colour whilst waiting for the perennials to spread out.
You may like to pop in a few beetroot, the foliage looks good and you will get an edible crop too of beets and the young leaves are good in a mixed salad.