Define "good". What are you aiming to achieve? What is the purpose of these tiles? is this top view, side view? Without knowing what you're trying to achieve, no one can tell you how well or poorly you've done.
Do you have a specific type of rock/texture you're going after? What's the scale on these? Are these pebbles seen from above, or the side of a cliff? Cliffs aren't usually made of a bunch of distinct rocks like this.
It really helps to set out to achieve something specific rather than thinking in vague terms like [rocks], and think in terms of entire environments, not elements in isolation. Look at cool environments in real life (and in games if you want), see how they come together. It takes more than a rock tile to make the ground look like pebbles and a cliff to look like a cliff. By observing real environments, you can learn what makes them feel/look like those environments.
