Make sure you have somewhere to sit. We put in a raised bed all down one side made from sleepers and filled with topsoil. It was deep.
I put in a rowan tree for height, a pittisporum for evergreen colour. A fatsia japonica spiderweb - lush evergreen. I had a lot of small shrubs/trees in pots - dwarf lilac, a kojo no mai blossom tree, a wisteria, a fig (big lush leaves and like being in a pot) and a couple of acers. Also ferns for a shady corner in pots. I had bulbs in pots so could move out the way when done their thing. And dahlias in huge pots as well as begonias - something like begonia fireworks or glowing embers. I hung big trough baskets on the wall so wouldn't need lots of watering.
And I put in a bronze fennel for height and lots of alliums. It was a very lush space.
The L bit of ours I put a lean to greenhouse in and used it to store pots that weren't being used as well. That was the dark bit of the yard for us.
I also made use of the back lane and planted a beautiful huge honescuckle that came back into our yard and a buddliea that the butterflies loved.
Top picks are the bigger the pot - the easier it is to grow things. Have somewhere to put the stuff while it's not looking its best and other gardening stuff.
I googled shady courtyard gardens, looked at the blog middle sized garden and subscribed to gardener's world.
Also... most things will grow in pots - just be prepared to pass them on to a good home when they out grow the pots.