that mountain on the right... the overhanging curved pointy bit looks a bit silly. i'd say make it a bit flatter like the other ones. right now it's just poo-shaped.
if you're putting this in an animation, some sandy wind effect might be a good touch if you can pull it off, maybe even just in the form of a light alpha sand-coloured gradient passing across the screen occasionally.
everything else i have to say has all been said already, but yeah:
- needs variation in the grass. don't be lazy and copy and paste it a bunch of times, just draw in a bit more new grass...
- the rock in the front, at least, really needs some more detail. i'd suggest adding more detail to the background rocks/mountains also
- a cactus or two might be a good touch
- a little bit of blur on the clouds could look good also.