what sun do you get? if you get full sun on a wall I would cover it in ornamental grape. Given it is a small space, perhaps espalier plants? You could get a large mirror suited to outdoors to create the illusion of more depth. I would stick to just maybe 2 or 3 plant choices

what a great space what about a very open pergola in front of the fence with lattice to exclude the most view of the neighbours and try some climbers (subject to climate) like Potato vine or Boston ivy or Virginia Creeper, paint the lower fence and the wall in a dark grey and add some nice big terra cotta pots with lots of herbs and veges and perhaps a lemon or olive tree...and of course, a barbq and great big table along the block wall

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I would create a tall wall of privacy along your back fence, perhaps by running a line of potted pencil pines, magnolia, or similar classic screening plant you might like. The pots become the feature then, with a line of trees giving nice symmetry and greenery there, while not detracting from your lovely paving which is a feature in itself (infact, the eye will run along this paving to that back fence, so I don't think the back fence should be too busy).

Your retaining wall could become your feature garden ie. you could cap it and then hang here your existing plants, a mirror, maybe even just a simple sculpture or fountain against that wall depending on your taste.

What is your taste Jannie, as perhaps Houzzers can give more specific suggestions if you nominate whether you prefer traditional, contemporary or minimalist outdoor rooms/gardens?

You planning on doing any Entertaining in the area?

For any entertaining purposes it may be good to add a Bar Style Top along the wall that is wide enough to then Store Stools out of the way underneath when not in Use. Saves Space in the Center but still allows people to eat and Drink outside..