Posted: 13/03/2016 at 10:16
You could simply make that one along the back deeper - about four feet. That will give you a lot more scope, or take a curve from the start of the left hand one across to meet the other side. Draw a simple plan on paper and play about with shapes if you want to make anything bigger.
It's hard to see in your pic but I assume that the 'rear' wall is stepped up at the right side to meet the right hand wall? You could have lower growing planting on the left side which would spill over the wall and soften it a bit. Roses might be good for there - I don't grow roses but you could start a specific thread for suggestions if you liked that idea. Carrying on with pansyface's suggestion, some of the smaller evergreen Azaleas would also be fine there.
Think about colour too - keep the flower colours to a minimum to avoid a clashing look, but if you want a riot of colour then go for it - and keep the foliage colour similar to avoid giving you a headache! A repeat of something like Hellebores will tie everything together, and you can also do that with bulbs for this time of year.