Croton if you are a zone 10 or higher SoCal.

how about a pic or two ...

whats the surface that limits the bed size.. are you considering reflected light in the equation? .. will retained and reflected heat be an issue? .. especially if large or huge transplants .. what is the soil type ...

not many plants die for lack of light.. they just have reduced vigor ... they might not grow as fast.. nor as thickly ... but eventually they will get the job done.. but it might take years ...

tress and shrubs have unique water needs and that can be difficult on drip irrigation ... youll need to figure that all out also ...

2 foot wide is not an easy place to grow things where you want this kind of height .. it might be many years or growing and pruning.. before you accomplish this goal ... nbd.. just making sure your expectations are in line with reality .. short of you paying big bucks for instant gratification ....

ken

Camellia bush?

2' is a very narrow planting bed!! Not much will fit in that very restricted space. A clumping bamboo could work but few, if any shrubs, are going to stay within size bounds AND tolerate shade as well.

How about an evergreen vine to climb up and cover the wall? I'm not sure if Hedera canariensis (variegated) will readily climb a wall, but could be trained. There are also the Persian ivies -- Hedera colchica 'Sulphur Heart' or 'Dentata Variegata' if they are appropriate for your zone. Probably many more climbers to choose from -- even nice flowering ones.

The hybrid x Fatshedera lizei (such as ‘Angyo Star’) generally wanders along the ground, but might be trainable on a wall with wires or support.

Clematis armandii may need just a bit of sun to bloom well. Also evergreen and flowers are oh so fragrant.

Also fragrant is Trachelospermum jasminoides, the Star Jasmine.