This is my first tutorial so be nice.
I will show you how to make some pretty cool backgrounds

Anyway
Start
First of all open a canvas with these settings:

Now, set your colours to white and black, with white on top.
Now do this on your first layer:

Outcome:

Now, new layer. And use brushes! Only use a brush "once". Once you've clicked one dont use it again.
Now, new layer, black brushes, and go over the white layer.
Outcome:

Now get your render out, and put it on your sig so far.

Now duplicate the render so it covers the WHOLE canvas. As many as it takes.
Outcome:

Now merge all of the render layers into ONE layer.
And do this:

Use these settings:

Outcome:

Now you need to make the layer overlay.

Now you should have a rather sexy outcome:

But it doesnt look that good yet, so we need to toy around with the colour settings.
Right click on the layer, and click blending options, and toy around until t suits you.

Now you should have a sexy background!!

Thanks for reading,
Sats