I am too exhausted this year from planting the front yard (CA natives, in winter) and the backyard (subtropicals, in spring) to get too excited about the back-back yard just yet.
Another year maybe? 2 years?
We're planning "drought-tolerant Mediterranean (mostly)" for that space. We've already planted fruit trees (which aren't necessarily drought-tolerant, but hey—we like fruit): 'Wonderful' pomegranate, 'Improved Meyer' lemon, 'Satsuma' mandarin, 'Panamint' nectarine, 'Santa Rosa' plum, and 'Flavor King' pluot. They've had varying degrees of success. Pomegranate = perfection. Lemon = loser. But I digress.
Some additional ideas for the back-back...
Brazilian Flame Vine:
Soft, hardy phlomis.
Pride of Madeira:
So as you can see: hotter/dryer plants, with an orange/yellow/red/purple palette. And then we'll be done with the yard... HAR.