Zone 8, mostly shade, southeast facing, caliche under the lean to

Hello Pros!

What could I plant for ground cover? Right now it's just caliche (think talcum powder texture, well almost). It's an extension of our living area to be used as our patio. The entire area measures 15' x 24' and is open on one short side/end and one long side. We will be only be able to add a very shallow layer of soil on top, but the caliche that's there can't be disturbed as it's up against our foundation. To excavate it might cause shifting of the foundation! Eeek! We may be able to amend it from about 18" - 24" from the slab and out.

So, given those specs, what could I plant? My thoughts: it could be partially done with some type of grass for shade with areas of another type ground cover (shade/some morning sun) in small, bordered "beds" and with stepping stones we'll make with concrete and a mold. I would prefer evergreen, or at least mostly evergreen - most of the year. We're in the Dallas area. Drought tolerant might be a good thing, as well..

Thanks so much!