does Lego make bricks with a stone, brick or concrete block design?
As usual with LEGO, the best solution is often to make your own.

You can make quite impressive brick walls using tiles, like this (image from Brickshelf):



There is a tutorial for something similar here.

A range of other techniques can be found in an article called Avoiding the "Big Gray Wall" Syndrome  at Classic-Castle.com. In fact, Google LEGO castles for a great source of inspiration for stonework of all kinds. For example, check this and this out.