You might be able to do something like this, but not with a procedural material. For the example, let's say it's the grid that you want to vary, so that the upper squares are more heavily "embossed" (have greater depth) than the lower squares of the grid. You'd need to start in your paint program, layering the grid and the gradient together until it's looking like you want, where the squares start off deep and become more shallow. Then you'd need to use that image for the material -- either as an image object, or perhaps as a terrain material (scroll down the forum a ways for Smallspace's post with the bricks). This wouldn't be exactly the sort of thing you're asking about, but with a bit of effort in the paint program, I think you could get close to it. :)