This is excellent info. Tagging @red51 to make sure he sees this.
The deserts do need quite a bit of work. I agree there needs to be seperate biomes for both east and west desert types. I want to say this is planned but I'm not 100% positive. I know there are more biomes (including a jungle and a swamp) and an overhauled world type are in the works. We definitely need more ground textures are needed: white sands for beaches and and other colored sands, standstones, and clays for a Painted Desert (with flat top mountains). There's a plan to implement loose rocks (for primitive crafting), so I want to say that large boulders would come too. These would also fit in with the American desert well.
I'm sure more plant life will come (i definitely want a prickly pear) and I agree with you on plants being closer to water. Probably once more stuff is added the code can be tweaked to improve the arrangement of plants.
Snakes and rats are already in the game but not activated yet. You can spawn them from the console if you want to check them out. I'm not sure if any variation of snakes is planned. Other animals are coming too (lion, horse, and gazelle for certain).
I'm curious now what your thoughts are on this. The other biomes seem to be sized just fine but i think for a desert, they need to be several times the size. I can usually stand in the middle of a desert and see some green at the edge of my viewing distance. I imagine something majestic like Monument Valley would probably dominate such a tiny desert biome and look rather odd.