I like the idea of these tiles, and what they could be, but the execution is a bit rough, a lot of technical issues hinder this piece.
The main problem for me is the banding. The rocks making up the cliff are so anti-aliased into themselves that they look too blurry and soft, instead of rough and rugged. In your shading technique there also seems to be a lot of random pixel placement. In the top middle of the cliff, there's a lot of vertical streaks that don't really fit into the rock structure. There's also some jaggies, especially around the top sand platform of the cliff.
Color is another problem that hinders this piece. The colors are too basic, and flat in terms of saturation, making it bland. There's high contrast between the cliff and the sand which is good to establish depth. But the problem here, is transition between that sand and cliff. IE, you have some grey AA on the bottom but not at the top of the cliff (though I understand it's a wip). I would drop that grey and go for a darkish orangey beige color. For the browns of the cliff, I would look into hue shifting for more dynamism. Browns can easily regress into reds and purples and progress into yellow.
The whole cliff wall is monotonous, in order to increase the illusion of depth, try to accentuate the sides of the walls (as well as the planes of the rocks, which seem muddled.) Depending on the lightsource, make one side darker, the main side neutral, and one side lighter. It looks you already tried this to an extent, but it should be more clearly stated. Also, I would curve the sides of the cliff more, or even make them rough diagonals because right now it looks too blocky.
As for the sand, it's good that it's low saturated, so the sprites don't get washed away in endless detail. Sand is a difficult texture to capture. I think studying old snes games like Seiken Densetsu 3, and Chrono Trigger can visually answer the idea better than I can articulate it.
I would say, that this is a good start. It reminds me of Romancing Saga 3's desert, which is another game you should study, as well as some of the desert landscapes in the Legcay of Goku series.
Hope this helped, sorry I don't have any visual examples/edits, but I tried to explain everything well enough. Also it would help if you showed sprites, or how some of this tiles, like the sand or the middle part of the cliff.