There are lots that would look good here, and other members will give you some ideas Firstly it looks shady? if it is how about Heucheras? I put 10 in an area about this size and the colour, interest they give is amazing.

What way does your garden face, what time of day was this pic taken am, midday or pm? :o)

The picture was taken this morning at 9.30am

My first thought was a climber on the fence and then a little white statuette in the middle with some ferns and heucheras round and spring bulbs underplanted. But if it gets full sun for a long time later in the day that might not work so well.

Possibly a good flowering shrub to cover the fence ; maybe a camellia or one of the scented viburnums if that suits the aspect. Then blocks of perennials and bulbs in front. Trailing nasturtiums maybe wandering along the front over the stones ; very easy and reliable. Or an edging of lavenders.

Or a good sized bird bath in the centre surrounded by something like apricot or orange coloured erysimums and blue hardy geraniums and lavenders.

But everyone's tastes are different.

Thanks everyone for your replies you all have given me some good ideas. I didn't know if covering the area in plum coloured slate would work with a few plants around and maybe a water feature in the centre. As we had this coloured slate around the pond before we removed it and we have the same coloured slate in borders already around the garden, what does everyone think ? Also we will be replacing the fence

Well it would work if you like slate - its really a question of what you prefer. It always seems to me to be a waste of good growing space to cover it with slate or pebbles but it is very fashionable just now and lots of people do like it.
Good luck with replacing the fence - hope getting behind the shrubs won't be too difficult.

I prefer plants , plants and more plants so I would have plenty of planting in the slate area so that the slates becomes a narrow walkway between the plants.

Good luck with it.

That's a fair compromise!