1, First make a new image, for this tutorial I am going to use a 500x500 image.

2, Fill it in gray and add noise with these settings

3, Add motion blur with an angle of 0 and a distance of 100. Round the edges there will be some white streaks
to get rid of this delete the edges of the image so crop a large square in the middle with no white streaks to get a proper
square hold down the shift while doing this. Then change the canvas size with the settings shows below....

4, Select quick mask mode (press q) and the draw a mask on with an soft airbrush and a high pressure.
Exit quick mask mode and then texturize it to give it a rough texture.

5, If you want add some dark and light patches with a larger airbrush with a low pressure.
Copy the image on to a new layer and then Filter -> Other -> Offset... offset the new layer with a wraparound
by about 150 pixels each way. You will notice that there are some seams up and across the image, here
comes the clever bit. Go into quick mask mode and the with a large soft air brush with 100 pressure go up
and across the seams. Exit quick mask mode and then delete the part that you selected (you may need to
invert the selection).

6. There you go the texture now tiles, wasn't that easy? You can add more things to this and end up with something
like this.