The sand seems to dirt-like. Some sands look like that in the world, but I like to see smoother flatter sand in art. The cloud in the top left looks like melting ice cream, and the sky overall looks uneven, considering the way the blue transforms to a darker blue. The 'dude's' right arm could've been more defined.

i have to disagree with etoria, the sand looks like sand to me. maybe showing the enlarged size picture can lead people to not visualize it in its original size, which can make them wonder that some shapes are wrong. you should post an original size pic just to not mislead people (just in case).

the sky and sand color (which aren't fully saturated) make this a moody pic. the clouds could have some antialias on the edges (not all of them though), to give them an impression that they're bluring out (practice practice practice)

i just noticed, the left leg has a dark pixel on the highlights side

I AM EMBARRASED
fixed this right away

and thanks for the orginial size tip, it has been added right next to the updated version of sand dude

Hey, you make pixel art too, cool.

The only thing that bothers me about the picture is the sky, I think it should fade more gradually. It would look cool if the light had some effect on its shading too

Also the two clouds and the guy's head together kinda looks like a pig. (Cannot be unseen)

You should totally make some 64-bit stuff.
also these would make really cool avatars if resized to 100kb
so you could like sell them as that and stuff