If you could mount some small eye bolts in the stones near the top to hang strings or wire from, you could have almost any climber/vine. Pole beans, sweet potatoes, cucurbits, climbing roses, or clematis come to mind.
What is your main objective - beauty, usefulness, or the bees? Do you prefer annual or perennial?
And that's when I realized I wasn't wearing any pants. Maybe this tiny ad has pants:
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