RailClone uses grid-like arrays so it's difficult to create a completely randomised and chaotic pattern one stone at a time. My usual solution is to create the illusion of randomised stones by "pre-composing" them into segments of interlocking geometry. For example by creating tetris-like blocks of random stones like this.
You can then use a Randomise operator to add these to an A2S array. The blocks are designed to interlock in an attempt to hide visible rows and columns. The more how have the less likely you are to see repetition and in the style you can also use Mirror and Transform operators to create even more randomisation. There's more information about this and some example files you can download in this forum post: http://forum.itoosoft.com/index.php?topic=2905.msg11141#msg11141
. Although this isn't for a gabion wall the same principles would apply except that you would also use a second generator for the wire mesh.
A similar approach is used in example1 from my previous post, please let me know if you'[re not able to download it.