I would advise a bit less noise in some areas, it seems a bit crowded for a background piece. Perhaps if the tan tiles are meant to be sand, they could be more smooth with a few rocks and extraneous bumps here and there. As for the plants, I would advise looking at some references on the site. A lot of the ones that I seem to find most interesting have more individual clusters of pixels as defined leaves, rather than stray pixels to represent leaves, if that makes any sense.
Hope I helped somewhat