This wall was made from, one 4'x8' OSB board, four 1"x2"x8' sticks, and a half bucket joint compound mix with dark gray house paint, all from The Home Depot. Total Cost for one section is about $15 dollars plus your time.
It is best if you invest in a drill motor paint stirrer. They are fairly cheap at Wal-Mart. Also remember that the joint compound color will be several shades lighter when it dries.
Take the joint compound and spread it out over the OSB board. We used a wood concrete hand float to spread and smooth it out. We had about an 1\8 inch thick of joint compound. About half a bucket worth.
We bought a random stone form from The Home Depot. It cost $9.89. Take the form and press it into the joint compound. You can also use a hammer to tap the form; this was a lot easier then pressing the form by hand. Repeat until the whole board is done
Then you will need to clean up the pattern lines.
We then air brushed in the grout lines.
(After making a couple of walls we figured out it is best to wait for the walls to be assembled before air brushing the grout lines. It was next to impossible to line up the grout lines when they were applied before the walls were assembled )
The first thing you need to do is attach the 1x2x8s to the OSB board, around the edges and two in the middle. This will add strength to the wall. Then you will need to paint the front side of the board with a dark color paint. The bad mix paint at The Home Depot will do just fine, and it's cheap. You need to do this to seal the wood.
