A design:

A couple queen palms and some semi-dwarf citrus would be nice. Looks like there was a vine on that wall at one time. You could train a grape vine there.

That planting strip is skinnier than is practical. Too skinny for many woody plants over a lengthy period of time. (I can't really imagine a queen palm fitting there.) If you want height, you might consider a tree form shrub that you can espalier against the wall and then allow it to grow above it as well ... sort of like you have the one in the corner. But really, you need to give the plants more room. How about papaya?

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2ft is pushing the limits, but here are some:

Cupressus sempervirens (Italian Cypress) - Many different cultivars to select from
Cupressus macrocarpa 'Wilma' (Monterey Cypress) -Very cool evergreen, wish I could grow it in my zone.
Buxus sempervirens 'Graham Blandy' (Upright Boxwood)
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That's about all I can think of. With the hornbeam or any fastgaita tree, the idea is to limb it up, so that the broader foliage occurs closer to the fence line, preserving space and preventing a "Boxed In" feeling.

I have seen Solanum laciniatum effectively used as a single trunked "tree" (a standard) in small spaces. It needs shearing at least once a year to keep it attractive. Attains about 7 feets here. Its purple color combines well. Underplanted with hot pink petunias would be a knockout. Dark colors recede, helping with depth. Also the trunk against a solid fence gives an effect not achieved by a shrub.

In a narrow bed in a small yard it's a shrub/s trained as a standard or doing an espalier as Yardvaark suggests. I have made my biggest, almost biggest, mistakes with narrow beds.