Hi there,
I am also currently researching the North African Campaign for a dio. It depends on where you set your scene, Basically the area consists of rock and sand. The Libyan desert is mostly a flat stretch of sand with rocky patches. To the west is the Atlas Mountains - Kasserine Pass, to the east the sand dunes only start in Egypt. The guys had to dig deep for cover in the desert. The southern extremities, bordering on the Sahara desert also has dunes, but only the LRDG went that far.
Sand and cat litter will give you a general desert effect. Since water in the desert is scarce, you will only find plants near oasis. Some areas did have small desert brush, barely ankle height and very sparse.